As filed with the Securities and Exchange Commission on March 27, 2026

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13E-3
RULE 13E-3 TRANSACTION STATEMENT UNDER SECTION 13(E)
OF THE SECURITIES ACT OF 1934
(Amendment No. 3)

Janus Henderson Group plc
(Name of the Issuer)

Janus Henderson Group plc

Jupiter Topco LLC

Jupiter Acquisition Limited

Jupiter Company Limited

Jupiter Merger Sub Limited

Trian Partners AM Holdco II, Ltd.

Trian Fund Management GP, LLC

Trian Fund Management, L.P.

Nelson Peltz

Peter W. May

(Names of Persons Filing Statement)

Common Stock, $1.50 par value per share

(Title of Class of Securities)

G4474Y214

(CUSIP Number of Class of Securities)

(Name, Address, and Telephone Number of Person Authorized to Receive Notices and Communications on Behalf
of the Persons Filing Statement)

This statement is filed in connection with (check the appropriate box):

a. x The filing of solicitation materials or an information statement subject to Regulation 14A, Regulation 14C or Rule 13e-3(c) under the Securities Exchange Act of 1934.

b. ¨ The filing of a registration statement under the Securities Act of 1933.

c. ¨ A tender offer.

d. ¨ None of the above.

Check the following box if the soliciting materials or information statement referred to in checking box (a) are preliminary copies: ¨

Check the following box if the filing is a final amendment reporting the results of the transaction: ¨

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of this transaction, passed upon the merits or fairness of this transaction, or passed upon the adequacy or accuracy of the disclosure in this transaction statement on Schedule 13E-3. Any representation to the contrary is a criminal offense

TABLE OF CONTENTS

Page

INTRODUCTION

This Amendment No.3 (this “Amendment No. 3”) to the Transaction Statement on Schedule 13E-3 (as amended, the “Transaction Statement”) is being filed with the U.S. Securities and Exchange Commission (the “SEC”) pursuant to Section 13(e) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), jointly by the following persons (each, a “Filing Person,” and collectively, the “Filing Persons”): (1) Janus Henderson Group plc, a Jersey corporation (“Janus Henderson” or the “Company”) and the issuer of the ordinary shares, par value $1.50 per share (the “Shares”), which is the subject of the Rule 13e-3 transaction; (2) Jupiter Topco LLC, a Jersey limited liability company (“Topco”); (3) Jupiter Acquisition Limited, a private limited company incorporated under the laws of Jersey and a wholly owned subsidiary of Topco (“Midco”); (4) Jupiter Company Limited, a private limited company incorporated in Jersey and a wholly owned subsidiary of Midco (“Parent”); (5) Jupiter Merger Sub Limited, a private limited company incorporated in Jersey and a wholly owned subsidiary of Parent (“Merger Sub”); (6) Trian Partners AM Holdco II, Ltd., a Cayman Islands exempted limited liability company (“Stockholder”); (7) Trian Fund Management GP, LLC, a Delaware limited liability company (“Trian Management GP”); (8) Trian Fund Management, L.P., a Delaware limited partnership (“Trian Management”); (9) Nelson Peltz, a citizen of the United States of America; and (10) Peter W. May, a citizen of the United States of America.

This Transaction Statement relates to the Agreement and Plan of Merger, dated as of December 21, 2025 (the “Original Merger Agreement”) as amended by Amendment No. 1 to the Agreement and Plan of Merger, dated as of March 24, 2026 (the “Amendment”) (as it may be further amended from time to time, the “Merger Agreement”), by and among Parent, Merger Sub and Janus Henderson. At the closing of the transaction, subject to the terms and conditions of the Merger Agreement, Merger Sub will be merged with and into Janus Henderson (the “Merger”), in accordance with the Companies (Jersey) Law 1991 (as it may be amended from time to time, the “Companies Law”), with Janus Henderson surviving the Merger as a wholly owned subsidiary of Parent.

At the effective time of the Merger (the “Effective Time”) each Share issued and outstanding immediately prior to the Effective Time (other than Shares directly owned and held by Parent, Merger Sub (including Shares transferred by the Stockholder, directly or indirectly, to Parent immediately prior to the Effective Time), Janus Henderson or any of their respective subsidiaries (other than shares held by Janus Henderson or its subsidiaries on behalf of third parties, the “Excluded Shares”)) will be cancelled and automatically converted into the right to receive $52.00 per Share in cash, subject to deduction for any required withholding taxes and without interest (the “Merger Consideration”). Outstanding equity awards of Janus Henderson will be converted into the right to receive cash or cash-based consideration (or such other consideration as may be agreed with an individual award holder).

Following the Effective Time, the Shares will be delisted from the New York Stock Exchange and deregistered under the Exchange Act, and Janus Henderson’s stockholders (other than the holders of Rollover Shares (as defined below) and the holders of the Shares subject to rollover, equity purchases or participation arrangements (as described below)) will cease to have any ownership interest in Janus Henderson.

Concurrently with and as a condition to Janus Henderson’s execution of the Original Merger Agreement, the Stockholder, which beneficially owned 31,867,800 Shares as of the date of this Transaction Statement, entered into a voting and rollover agreement with Janus Henderson, Parent and two newly formed Jersey entities associated with Trian (the “Voting and Rollover Agreement”), pursuant to which the Stockholder, subject to certain limitations, committed to vote its Shares in favor of, and take certain other actions in furtherance of, the transactions contemplated by the Merger Agreement, including the Merger, and directly or indirectly contribute a portion of its Shares through a series of contributions involving the two newly formed Jersey entities that would result in Parent directly holding such contributed Shares immediately prior to the Merger (the “Rollover Shares”). The Stockholder’s voting obligations are subject to certain exceptions, including a change in recommendation by the board of directors of Janus Henderson (the “Board”) in accordance with the terms of the Merger Agreement. Subject to the terms therein, the Voting and Rollover Agreement will terminate upon the earliest to occur of (i) the mutual written agreement of Parent, Janus Henderson and the Stockholder, (ii) the Effective Time or (iii) the termination of the Merger Agreement in accordance with its terms.

In addition, the Merger Agreement provides that, following receipt of the Required Company Vote (as defined below) and subject to compliance with applicable law, Parent may make available to employees of the Company capacity for rollover and other equity purchases and/or participation opportunities, such employees to be identified based on their expressed interest and in consultation with senior management of the Company, provided that no such opportunity shall create any obligation or other liability of the Company prior to the closing.

The Board formed a special committee (the “Special Committee”) comprised solely of independent, disinterested members of the Board to, among other things, review, evaluate and negotiate the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger. The Special Committee, acting with the advice of its own independent legal and financial advisors, unanimously determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are in the best interests of Janus Henderson. Furthermore, the Special Committee recommended that the Board (i) resolve as required by Article 127E(1) of the Companies Law in the opinion of the directors voting for the resolution, that the Merger Agreement and the transactions contemplated thereby (including the Merger) are in the best interests of the Company; (ii) approve, adopt and declare advisable the Merger Agreement and the transactions contemplated thereby (including the Merger); (iii) direct that the approval and adoption of the Merger Agreement (including the Merger) be submitted to a vote at a meeting of Janus Henderson’s shareholders; (iv) recommend the approval and adoption of the Merger Agreement (including the Merger) by Janus Henderson’s shareholders pursuant to Article 127F(1) of the Companies Law; and (v) approve, adopt and declare advisable the Voting and Rollover Agreement and the limited guarantees.

The Board, other than certain directors recusing themselves in accordance with applicable law, (i) carefully reviewed and considered the terms and conditions of the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger; (ii) considered the unanimous recommendation of the Special Committee and such other matters as the Board considered necessary or appropriate; (iii) by a unanimous vote (other than those directors recusing themselves in accordance with applicable law) (a) resolved as required by Article 127E(1) of the Companies Law in the opinion of the directors voting for the resolution, that the Merger Agreement and the transactions contemplated thereby (including the Merger) are in the best interests of Janus Henderson; (b) approved, adopted and declared advisable the Merger Agreement and the transactions contemplated thereby (including the Merger); (c) directed that the approval and adoption of the Merger Agreement (including the Merger) be submitted to a vote at a meeting of Janus Henderson’s shareholders; and (d) recommended the approval and adoption of the Merger Agreement (including the Merger) by Janus Henderson’s shareholders pursuant to Article 127F(1) of the Companies Law. Such approval by the Board constituted approval by a majority of the directors of Janus Henderson directors who are not employees of Janus Henderson.

At an extraordinary general meeting (the “Special Meeting”) of Janus Henderson’s shareholders, Janus Henderson’s shareholders will be asked to, among other things, vote upon the proposal to approve and adopt the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger. The proposal to approve and adopt the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger, requires approval by special resolution. This means that, for this resolution to be passed, at least two-thirds (2/3) of the total number of votes cast at the Special Meeting must be cast in favor of this resolution (the “Required Company Vote”). The failure to vote or the abstention from voting will have no effect on the proposal to approve and adopt the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger.

On March 11, 2026, the Company filed a definitive proxy statement (the “Definitive Proxy Statement”) under Regulation 14A of the Exchange Act with the SEC relating to the Special Meeting. The Proxy Statement is attached hereto as Exhibit (a)(i). A copy of the Merger Agreement is attached to the Definitive Proxy Statement as Annex A. Concurrently with the filing of this Amendment No. 3, the Company is filing definitive additional materials under Regulation 14A of the Exchange Act (the “Supplement”). The Supplement is attached hereto as Exhibit (a)(xxxiv). A copy of the Amendment is attached to the Supplement as Annex A. The Definitive Proxy Statement as amended and supplemented by the Supplement is referred to as the “Proxy Statement.” Terms used but not defined in this Transaction Statement have the meanings assigned to them in the Proxy Statement.

Pursuant to General Instruction F to Schedule 13E-3, the information in the Proxy Statement, including all annexes thereto, is expressly incorporated by reference herein in its entirety, and responses to each item herein are qualified in their entirety by the information contained in the Proxy Statement. The cross-references below are being supplied pursuant to General Instruction G to Schedule 13E-3 and show the location in the Proxy Statement of the information required to be included in response to the items of Schedule 13E-3.

While each of the Filing Persons acknowledges that the Merger is a “going private” transaction for purposes of Rule 13e-3 under the Exchange Act, the filing of this Transaction Statement shall not be construed as an admission by any Filing Person, or by any affiliate of a Filing Person, that the Company is “controlled” by any of the Filing Persons and/or their respective affiliates.

The information concerning the Company contained in, or incorporated by reference into, this Transaction Statement and the Proxy Statement was supplied by the Company. Similarly, all information concerning each other Filing Person contained in, or incorporated by reference into, this Transaction Statement and the Proxy Statement was supplied by such Filing Person. No Filing Person, including the Company, is responsible for the accuracy of any information supplied by any other Filing Person.

Item 1. Summary Term Sheet

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

Item 2. Subject Company Information

(a) Name and address.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet—The Parties—Janus Henderson”

“Parties to the Merger—Janus Henderson”

“Important Information Regarding Janus Henderson”

“Where You Can Find More Information”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Important Information Regarding Janus Henderson”

“Where You Can Find More Information”

(b) Securities.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet—The Merger”

“Summary Term Sheet—Shareholders Entitled to Vote; Vote Required to Approve the Merger and the Other Transactions Contemplated by the Merger Agreement”

“Questions and Answers About the Special Meeting and the Merger”

“The Special Meeting—Record Date and Quorum”

“Important Information Regarding Janus Henderson—Company Background”

“Important Information Regarding Janus Henderson—Security Ownership of Certain Beneficial Owners and Management”

“Important Information Regarding Janus Henderson—Market Price of Janus Henderson Shares”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet—Amendment to Merger Agreement”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Important Information Regarding Janus Henderson—Market Price of Janus Henderson Shares”

(c) Trading market and price.

The information set forth in the Definitive Proxy Statement under the following caption is incorporated herein by reference:

“Important Information Regarding Janus Henderson—Market Price of Janus Henderson Shares”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Important Information Regarding Janus Henderson—Market Price of Janus Henderson Shares”

(d) Dividends.

The information set forth in the Definitive Proxy Statement under the following caption is incorporated herein by reference:

“Important Information Regarding Janus Henderson—Dividends”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Important Information Regarding Janus Henderson—Dividends”

(e) Prior public offerings.

The information set forth in the Definitive Proxy Statement under the following caption is incorporated herein by reference:

“Important Information Regarding Janus Henderson—Prior Public Offerings”

(f) Prior share purchases.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Important Information Regarding Janus Henderson—Prior Public Offerings”

“Important Information Regarding Janus Henderson—Transactions in Janus Henderson Shares”

“Important Information Regarding Janus Henderson—Past Contacts, Transactions, Negotiations and Agreements”

Item 3. Identity and Background of Filing Person

(a) — (c) Name and Address of Each Filing Person; Business and Background of Entities; Business and Background of Natural Persons.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet—The Parties”

“Parties to the Merger”

“Important Information Regarding Janus Henderson”

“Important Information Regarding the Buyer Filing Parties”

“Where You Can Find More Information”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Important Information Regarding Janus Henderson”

“Where You Can Find More Information”

Item 4. Terms of the Transaction

(a) — (1) Material terms. Tender offers. Not applicable.

(a) — (2) Mergers or Similar Transactions.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Unaudited Prospective Financial Information”

“Special Factors—Opinion of Goldman Sachs & Co. LLC”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Consequences If the Merger Is Not Completed”

“Special Factors—U.K. Tax Considerations”

“Special Factors—U.S. Federal Income Tax Considerations for U.S. Holders”

“Special Factors—Accounting Treatment”

“Special Factors—Delisting and Deregistration of Janus Henderson Shares”

“The Special Meeting—Vote Required for Approval”

“The Agreement and Plan of Merger—Merger Consideration”

“The Agreement and Plan of Merger—Treatment of Outstanding Equity Awards”

“The Agreement and Plan of Merger—Exchange of Certificates”

“The Agreement and Plan of Merger—Conditions to the Merger”

Annex A — Agreement and Plan of Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Opinion of Goldman Sachs & Co. LLC”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Intent of Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Consequences If the Merger Is Not Completed”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger 

(c) Different terms.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Financing”

“Special Factors—Limited Guarantee”

“Proposal 3: Non-Binding Compensation Advisory Proposal”

“The Agreement and Plan of Merger—Merger Consideration”

“The Agreement and Plan of Merger—Treatment of Outstanding Equity Awards”

“The Agreement and Plan of Merger—Exchange of Certificates”

“The Agreement and Plan of Merger —Employee Benefits”

“The Agreement and Plan of Merger —Director and Officer Indemnification and Insurance”

“The Agreement and Plan of Merger—Miscellaneous—Special Committee Compensation”

“Voting and Rollover Agreement”

Annex A—Agreement and Plan of Merger

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Financing”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger 

(d) Appraisal rights.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet—Right to Object”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Right to Object”

“Dissenters’ Rights and Rights of Objecting Shareholders”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Right to Object”

(e) Provisions for unaffiliated security holders.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet—Recommendation of the Special Committee; Recommendation of the Board; Reasons for Recommending the Approval and Adoption of the Merger Agreement and the Transactions Contemplated by the Merger Agreement, Including the Merger”

“Summary Term Sheet—Right to Object”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Right to Object”

“Dissenters’ Rights and Rights of Objecting Shareholders”

“Provisions for Unaffiliated Security Holders”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Right to Object”

(f) Eligibility for listing or trading. Not applicable.

Item 5. Past Contacts, Transactions, Negotiations and Agreements

(a) Transactions.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Background of the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Financing”

“Special Factors—Limited Guarantee”

“Proposal 3: Non-Binding Compensation Advisory Proposal”

“The Agreement and Plan of Merger”

“Voting and Rollover Agreement”

“Important Information Regarding Janus Henderson—Prior Public Offerings”

“Important Information Regarding Janus Henderson—Transactions in Janus Henderson Shares”

“Important Information Regarding Janus Henderson—Past Contacts, Transactions, Negotiations and Agreements”

“Important Information Regarding the Buyer Filing Parties”

Annex A—Agreement and Plan of Merger

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Financing”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger 

(b) —(c) Significant corporate events; Negotiations or contacts.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“Special Factors—Financing”

“Proposal 3: Non-Binding Compensation Advisory Proposal”

“The Agreement and Plan of Merger”

“Voting and Rollover Agreement”

“Important Information Regarding Janus Henderson—Past Contacts, Transactions, Negotiations and Agreements”

Annex A—Agreement and Plan of Merger

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Financing”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger 

(e) Agreements involving the subject company’s securities.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Financing”

“Special Factors—Limited Guarantee”

“Proposal 3: Non-Binding Compensation Advisory Proposal”

“The Agreement and Plan of Merger”

“Voting and Rollover Agreement”

“Important Information Regarding Janus Henderson—Transactions in Janus Henderson Shares”

“Important Information Regarding Janus Henderson—Past Contacts, Transactions, Negotiations and Agreements”

Annex A—Agreement and Plan of Merger

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Financing”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger 

Item 6. Purposes of the Transaction, and Plans or Proposals

(b) Use of securities acquired.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Plans for the Company After the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Consequences If the Merger Is Not Completed”

“Special Factors—Financing”

“Special Factors—Delisting and Deregistration of Janus Henderson Shares”

“The Agreement and Plan of Merger—Merger Consideration”

“The Agreement and Plan of Merger—Treatment of Outstanding Equity Awards”

“The Agreement and Plan of Merger—Exchange of Certificates”

Annex A—Agreement and Plan of Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Consequences If the Merger Is Not Completed”

“Update to Special Factors—Update to Financing”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger 

(c) (1) — (8) Plans.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Plans for the Company After the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of the Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Consequences If the Merger Is Not Completed”

“Special Factors—Financing”

“Special Factors—Limited Guarantee”

“Special Factors—Delisting and Deregistration of Janus Henderson Shares”

“The Agreement and Plan of Merger”

“Important Information Regarding Janus Henderson”

Annex A—Agreement and Plan of Merger

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Intent of the Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Consequences If the Merger Is Not Completed”

“Update to Special Factors—Update to Financing”

“Update to Important Information Regarding Janus Henderson”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger 

Item 7. Purposes, Alternatives, Reasons and Effects

(a) Purposes.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Plans for the Company After the Merger”

“Special Factors—Certain Effects of the Merger”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

(b) Alternatives. The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Consequences If the Merger Is Not Completed”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Consequences If the Merger Is Not Completed”

(c) Reasons. The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Unaudited Prospective Financial Information”

“Special Factors—Opinion of Goldman Sachs & Co. LLC”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Consequences If the Merger Is Not Completed”

Annex C—Opinion of Goldman Sachs & Co. LLC

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Opinion of Goldman Sachs & Co. LLC”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Consequences If the Merger Is Not Completed”

Annex B—Opinion of Goldman Sachs & Co. LLC

(d) Effects. The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Opinion of Goldman Sachs & Co. LLC”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Plans for the Company After the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Certain Effects of the Merger”

“Special Factors—Consequences If the Merger Is Not Completed”

“Special Factors—Right to Object”

“Special Factors—U.K. Tax Considerations”

“Special Factors—U.S. Federal Income Tax Considerations for U.S. Holders”

“Special Factors—Financing”

“Special Factors—Delisting and Deregistration of Janus Henderson Shares”

“Special Factors—Fees and Expenses”

“Proposal 3: Non-Binding Compensation Advisory Proposal”

“The Agreement and Plan of Merger—Treatment of Outstanding Equity Awards”

“The Agreement and Plan of Merger—Employee Benefits”

“The Agreement and Plan of Merger—Director and Officer Indemnification and Insurance”

“The Agreement and Plan of Merger—Expenses; Termination Fees”

“Dissenters’ Rights and Rights of Objecting Shareholders”

Annex A—Agreement and Plan of Merger

Annex C—Opinion of Goldman Sachs & Co. LLC

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Opinion of Goldman Sachs & Co. LLC”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

“Update to Special Factors—Update to Consequences If the Merger Is Not Completed”

“Update to Special Factors—Right to Object”

“Update to Special Factors—Update to Financing”

Annex A—Amendment No. 1 to Agreement and Plan of Merger”

Annex B—Opinion of Goldman Sachs & Co. LLC

Item 8. Fairness of the Transaction

(a) — (b) Fairness; Factors considered in determining fairness.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Opinion of Goldman Sachs & Co. LLC”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Certain Effects of the Merger”

“The Special Meeting—Vote Required for Approval”

Annex C—Opinion of Goldman Sachs & Co. LLC

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Opinion of Goldman Sachs & Co. LLC”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

Annex B—Opinion of Goldman Sachs & Co. LLC

The discussion materials dated December 1, 2025, December 2, 2025, December 4, 2025, December 10, 2025, December 11, 2025, December 15, 2025, December 16, 2025, December 21, 2025, March 3, 2026, March 10, 2026, March 23, 2026 and March 23, 2026 prepared by Goldman Sachs & Co. LLC and reviewed by the Special Committee are filed as Exhibits (c)(i) – (c)(xii) and incorporated herein by reference.

(c) Approval of security holders.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“The Special Meeting—Record Date and Quorum”

“The Special Meeting—Vote Required for Approval”

“The Special Meeting—How to Vote”

“The Special Meeting—Revocation of Proxies”

“Proposal 1: Approval and Adoption of the Merger Agreement and the Transactions Contemplated by the Merger Agreement, Including the Merger”

“The Agreement and Plan of Merger—Conditions to the Merger”

Annex A—Agreement and Plan of Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger

(d) Unaffiliated representative.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Opinion of Goldman Sachs & Co. LLC”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Provisions for Unaffiliated Security Holders”

Annex C—Opinion of Goldman Sachs & Co. LLC

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Opinion of Goldman Sachs & Co. LLC”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

Annex B—Opinion of Goldman Sachs & Co. LLC

(e) Approval of directors.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Merger and the Special Meeting”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Intent of Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

(f) Other offers.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

Item 9. Reports, Opinions, Appraisals and Negotiations

(a) — (b) Report, opinion or appraisal; Preparer and summary of the report, opinion or appraisal.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Opinion of Goldman Sachs & Co. LLC”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Where You Can Find More Information”

Annex C—Opinion of Goldman Sachs & Co. LLC

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Opinion of Goldman Sachs & Co. LLC”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Where You Can Find More Information”

Annex B—Opinion of Goldman Sachs & Co. LLC

The discussion materials dated December 1, 2025, December 2, 2025, December 4, 2025, December 10, 2025, December 11, 2025, December 15, 2025, December 16, 2025, December 21, 2025, March 3, 2026, March 10, 2026, March 23, 2026 and March 23, 2026 prepared by Goldman Sachs & Co. LLC and reviewed by the Special Committee are filed as Exhibits (c)(i) – (c)(xii) and incorporated herein by reference.

(c) Availability of documents. The reports, opinions or appraisals referenced in this Item 9 will be made available for inspection and copying at the principal executive offices of the Company during its regular business hours by any interested equity holder of the Company or by a representative who has been so designated in writing.

Item 10. Source and Amounts of Funds or Other Consideration

(a) — (b) Source of funds; Conditions.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Financing”

“Special Factors—Limited Guarantee”

“The Agreement and Plan of Merger—Covenants Regarding Conduct of Business by the Company and Its Subsidiaries Prior to the Merger—Financing Cooperation”

“The Agreement and Plan of Merger—Conditions to the Merger”

“The Agreement and Plan of Merger—Other Covenants and Agreements”

Annex A—Agreement and Plan of Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Special Factors—Update to Financing”

Annex A—Amendment No. 1 to Agreement and Plan of Merger

(c) Expenses.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger—Special Committee Fees”

“Special Factors—Consequences If the Merger Is Not Completed”

“Special Factors—Fees and Expenses”

“The Special Meeting—Solicitation of Proxies”

“The Agreement and Plan of Merger—Expenses; Termination Fees”

“The Agreement and Plan of Merger—Miscellaneous—Special Committee Compensation”

Annex A—Agreement and Plan of Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Consequences if the Merger is Not Completed”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger

(d) Borrowed funds.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Financing”

“The Agreement and Plan of Merger— Covenants Regarding Conduct of Business by the Company and Its Subsidiaries Prior to the Merger—Financing Cooperation”

Annex A—Agreement and Plan of Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Special Factors—Update to Financing”

Annex A—Amendment No. 1 to Agreement and Plan of Merger

Item 11. Interest in Securities of the Subject Company

(a) Securities ownership.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“Voting and Rollover Agreement”

“Important Information Regarding Janus Henderson—Security Ownership of Certain Beneficial Owners and Management”

“Important Information Regarding the Buyer Filing Parties”

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

(b) Securities transactions.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Special Factors—Background of the Merger”

“The Agreement and Plan of Merger”

“Voting and Rollover Agreement”

“Important Information Regarding Janus Henderson—Prior Public Offerings”

“Important Information Regarding Janus Henderson—Transactions in Janus Henderson Shares”

Annex A—Agreement and Plan of Merger

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Special Factors—Update to Background of the Merger”

“Summary of Amendment to the Merger Agreement; Update to the Agreement and Plan of Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger

Item 12. The Solicitation or Recommendation

(d) Intent to tender or vote in a going-private transaction.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Intent of Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

“Special Factors—Intent of Certain Shareholders to Vote in Favor of the Merger”

“The Special Meeting—Vote Required for Approval”

“Voting and Rollover Agreement”

Annex A—Agreement and Plan of Merger

Annex B—Voting and Rollover Agreement

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Intent of Janus Henderson’s Directors and Executive Officers to Vote in Favor of the Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger

(e) Recommendation of others.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Proposal 1: Approval and Adoption of the Merger Agreement and the Transactions Contemplated by the Merger Agreement, Including the Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

Item 13. Financial Information

(a) Financial statements. The audited consolidated financial statements set forth in Item 8 of the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025 are incorporated herein by reference.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Special Factors—Unaudited Prospective Financial Information”

“Special Factors—Certain Effects of the Merger”

“Important Information Regarding Janus Henderson—Selected Historical Financial Data”

“Important Information Regarding Janus Henderson—Book Value Per Share”

“Where You Can Find More Information”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Special Factors—Update to Certain Effects of the Merger”

(b) Pro forma information. Not applicable.

Item 14. Persons/Assets, Retained, Employed, Compensated or Used

(a) — (b) Solicitations or recommendations; Employees and corporate assets.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers About the Special Meeting and the Merger”

“Special Factors—Background of the Merger”

“Special Factors—Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Special Factors—Reasons of the Buyers for the Merger”

“Special Factors—Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Fees and Expenses”

“The Special Meeting—Solicitation of Proxies”

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Questions and Answers About the Special Meeting and the Merger”

“Update to Special Factors—Update to Background of the Merger”

“Update to Special Factors—Update to Reasons for the Merger; Recommendation of the Special Committee and the Company’s Board of Directors”

“Update to Special Factors—Update to Reasons of the Buyers for the Merger”

“Update to Special Factors—Update to Position of the Buyer Filing Parties as to the Fairness of the Merger”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

Item 15. Additional Information

(b) Golden Parachute Compensation.

The information set forth in the Definitive Proxy Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Special Factors—Interests of Directors and Executive Officers in the Merger”

“Special Factors—Certain Effects of the Merger”

“Proposal 3: Non-Binding Compensation Advisory Proposal”

“The Agreement and Plan of Merger—Treatment of Outstanding Equity Awards”

Annex A—Agreement and Plan of Merger

The information set forth in the Supplement under the following captions is incorporated herein by reference:

“Update to Summary Term Sheet”

“Update to Special Factors—Update to Interests of Directors and Executive Officers in the Merger”

“Update to Special Factors—Update to Certain Effects of the Merger”

Annex A—Amendment No. 1 to Agreement and Plan of Merger

(c) Other material information.

The information set forth in the Definitive Proxy Statement, including all annexes thereto, is incorporated herein by reference.

Item 16. Exhibits

The following exhibits are filed herewith:

(a)(i) Definitive Proxy Statement of Janus Henderson Group plc (included in the Schedule 14A filed on March 11, 2026 and incorporated herein by reference).

(a)(ii) Form of Proxy Card (included in the Definitive Proxy Statement and incorporated herein by reference).

(a)(iii) Letter to Shareholders (included in the Definitive Proxy Statement and incorporated herein by reference).

(a)(iv) Notice of Extraordinary General Meeting (included in the Supplement and incorporated herein by reference).

(a)(v) Current Report on Form 8-K, dated December 22, 2025 (included in Schedule 14A filed on December 22, 2025 and incorporated herein by reference).

(a)(vi) Press Release, dated December 22, 2025 (included in Schedule 14A filed on December 22, 2025 and incorporated herein by reference).

(a)(vii) CEO Letter to Employees, dated December 22, 2025 (included in Schedule 14A filed on December 22, 2025 and incorporated herein by reference).

(a)(viii) Transcript of CEO Video Message for Employees, dated December 22, 2025 (included in Schedule 14A filed on December 22, 2025 and incorporated herein by reference).

(a)(ix) LinkedIn Post, dated December 22, 2025 (included in Schedule 14A filed on December 22, 2025 and incorporated herein by reference).

(a)(x) Janus Henderson Letter to Clients, dated December 22, 2025 (included in Schedule 14A filed on December 29, 2025 and incorporated herein by reference).

(a)(xi) Press Release, dated February 26, 2026 (included in Schedule 14A filed on February 27, 2026 and incorporated herein by reference).

(a)(xii) Employee Communication from February 26, 2026 (included in Schedule 14A filed on February 27, 2026 and incorporated herein by reference).

(a)(xiii) Janus Henderson Letter to Clients from March 2, 2026 (included in Schedule 14A filed on March 2, 2026 and incorporated herein by reference).

(a)(xiv) CEO Letter to Employees from March 3, 2026 (included in Schedule 14A filed on March 3, 2026 and incorporated herein by reference).

(a)(xv) Press Release, dated March 11, 2026 (included in Schedule 14A filed on March 11, 2026 and incorporated herein by reference).

(a)(xvi) Press Release of Trian Fund Management, dated March 11, 2026 (included in Schedule 14A filed on March 11, 2026 and incorporated herein by reference).

(a)(xvii) CEO Letter to Employees from March 11, 2026 (included in Schedule 14A filed on March 11, 2026 and incorporated herein by reference).

(a)(xviii) Janus Henderson Letter to Clients from March 11, 2026 (included in Schedule 14A filed on March 11, 2026 and incorporated herein by reference).

(a)(xix) LinkedIn Post of Trian Fund Management, dated March 11, 2026 (included in Schedule 14A filed on March 11, 2026 and incorporated herein by reference).

(a)(xx) Press Release, dated March 17, 2026 (included in Schedule 14A filed on March 17, 2026 and incorporated herein by reference).

(a)(xxi) Employee Communication from March 17, 2026 (included in Schedule 14A filed on March 18, 2026 and incorporated herein by reference).

(a)(xxii) Pages from Website Published on March 18, 2026 (included in Schedule 14A filed on March 19, 2026 and incorporated herein by reference).

(a)(xxiii) Janus Henderson Letter to Clients from March 19, 2026 (included in Schedule 14A filed on March 19, 2026 and incorporated herein by reference).

(a)(xxiv) Press Release and Investor Presentation of Trian Fund Management, dated March 20, 2026 (included in Schedule 14A filed on March 20, 2026 and incorporated herein by reference).

(a)(xxv) LinkedIn Post of Trian Fund Management, dated March 20, 2026 (included in Schedule 14A filed on March 23, 2026 and incorporated herein by reference).

(a)(xxvi) Press Release, dated March 24, 2026 (included in Schedule 14A filed on March 24, 2026 and incorporated herein by reference).

(a)(xxvii) Employee Communication from March 24, 2026 (included in Schedule 14A filed on March 24, 2026 and incorporated herein by reference).

(a)(xxviii) Janus Henderson Letter to Clients from March 24, 2026 (included in Schedule 14A filed on March 24, 2026 and incorporated herein by reference).

(a)(xxvix) Pages from Website Updated on March 24, 2026 (included in Schedule 14A filed on March 24, 2026 and incorporated herein by reference).

(a)(xxx) Current Report on Form 8-K, dated March 24, 2026 (included in Schedule 14A filed on March 24, 2026 and incorporated herein by reference).

(a)(xxxi) LinkedIn Post of Trian Fund Management, dated March 24, 2026 (included in Schedule 14A filed on March 24, 2026 and incorporated herein by reference).

(a)(xxxii) Employee Communication from March 25, 2026 (included in Schedule 14A filed on March 25, 2026 and incorporated herein by reference).

(a)(xxxiii) Janus Henderson Letter to Clients from March 25, 2026 (included in Schedule 14A filed on March 25, 2026 and incorporated herein by reference).

(a)(xxxiv) Current Report on Form 8-K, dated March 25, 2026 (included in Schedule 14A filed on March 25, 2026 and incorporated herein by reference).

(a)(xxxv) Supplement to the Definitive Proxy Statement of Janus Henderson Group plc (included in the Schedule 14A filed on March 27, 2026 and incorporated herein by reference).

(a)(xxxvi) Letter to Shareholders (included in the Supplement and incorporated herein by reference).

(a)(xxxvii) Notice of Extraordinary General Meeting (included in the Supplement and incorporated herein by reference).

(b)(i) Preferred Equity Commitment Letter, dated as of December 21, 2025, by and among Massachusetts Mutual Life Insurance Company and Jupiter Parent Limited (included as Exhibit 99.1 of the Schedule 13D filed by Massachusetts Mutual Life Insurance Company on December 23, 2025).

(b)(ii)+ Debt Commitment Letter, dated as of December 21, 2025, by and among Jupiter Borrower, Inc., Jupiter Company Limited, JPMorgan Chase Bank, N.A., Citigroup Global Markets Inc., Bank of America, N.A., BofA Securities, Inc., Jefferies Finance LLC, MUFG Bank, Ltd. and Sumitomo Mitsui Banking Corporation.

(b)(iii)+ Letter Agreement to Commitment Letter and Fee Letter, dated as of January 21, 2026, by and among Jupiter Borrower, Inc., Jupiter Company Limited, JPMorgan Chase Bank, N.A., Citigroup Global Markets Inc., Bank of America, N.A., BofA Securities, Inc., Jefferies Finance LLC, MUFG Bank, Ltd., Sumitomo Mitsui Banking Corporation, UBS AG, Stamford Branch, UBS Securities LLC and Morgan Stanley Senior Funding, Inc.

(b)(iv) Amendment No. 1 to Commitment Letter and Fee Letter, dated as of March 24, 2026, by and among Jupiter Borrower, Inc., Jupiter Company Limited, JPMorgan Chase Bank, N.A., Citigroup Global Markets Inc., Bank of America, N.A., BofA Securities, Inc., Jefferies Finance LLC, MUFG Bank, Ltd., Sumitomo Mitsui Banking Corporation, UBS AG, Stamford Branch, UBS Securities LLC and Morgan Stanley Senior Funding, Inc.

(c)(i)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 1, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.⸸

(c)(ii)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 2, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.⸸

(c)(iii)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 4, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(iv)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 10, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(v)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 11, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(vi)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 15, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(vii)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 16, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(viii)+ Discussion materials prepared by Goldman Sachs & Co. LLC, dated December 21, 2025, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(ix) ++Discussion materials prepared by Goldman Sachs & Co. LLC dated March 3, 2026, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(x) ++Discussion materials prepared by Goldman Sachs & Co. LLC dated March 10, 2026, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(xi) Discussion materials prepared by Goldman Sachs & Co. LLC dated March 23, 2026, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(c)(xii) Discussion materials prepared by Goldman Sachs & Co. LLC dated March 23, 2026, for the Special Committee of the Board of Directors of Janus Henderson Group plc.

(d)(i) Agreement and Plan of Merger, dated as of December 21, 2025, by and among Janus Henderson Group plc, Jupiter Company Limited and Jupiter Merger Sub Limited (included as Annex A to the Definitive Proxy Statement and incorporated herein by reference).

(d)(ii) Voting and Rollover Agreement, dated as of December 21, 2025, by and among Janus Henderson Group plc and Stockholders party thereto (included as Annex B to the Definitive Proxy Statement and incorporated herein by reference).

(d)(iii) Equity Commitment Letter, dated as of December 21, 2025, from Jupiter Core Holdings, L.P., Jupiter AM Investors, L.P., Trian Partners AM Fund, L.P. and Trian Partners AM Parallel Fund, L.P. (included as Exhibit 11 of Amendment No. 15 to Schedule 13D filed by Trian Fund Management, L.P. on December 22, 2025).⸸

(d)(iv)+ Equity Commitment Letter, dated as of December 21, 2025, from GC Jupiter Investor, LP.

(d)(v)+ Equity Commitment Letter, dated as of December 21, 2025, from Qatar Holding LLC.

(d)(vi)+ Limited Guarantee, dated as of December 21, 2025, from Trian Partners AM Holdco II, Ltd., Jupiter Core Holdings, L.P., Jupiter AM Investors, L.P., Trian Partners AM Fund, L.P. and Trian Partners AM Parallel Fund, L.P., in favor of Janus Henderson Group plc.⸸

(d)(vii)+ Limited Guarantee, dated as of December 21, 2025, from GC Jupiter Investor, LP, in favor of Janus Henderson Group plc.

(d)(viii)+ Limited Guarantee, dated as of December 21, 2025, from Qatar Holding LLC, in favor of Janus Henderson Group plc.

(d)(ix) Amendment No. 1 to the Agreement and Plan of Merger, dated as of March 24, 2026, by and among Janus Henderson Group plc, Jupiter Company Limited and Jupiter Merger Sub Limited (included as Annex A to the Supplement and incorporated herein by reference).

(d)(x) Amended and Restated Equity Commitment Letter, dated as of March 24, 2026, from Jupiter Core Holdings, L.P., Jupiter AM Investors, L.P., Trian Partners AM Fund, L.P. and Trian Partners AM Parallel Fund, L.P. (included as Exhibit 13 of Amendment No. 16 to Schedule 13D filed by Trian Fund Management, L.P. on March 24, 2026).⸸

(d)(xi) Amended and Restated Equity Commitment Letter, dated as of March 24, 2026, from GC Jupiter Investor, LP.

(d)(xii) Amended and Restated Limited Guarantee, dated as of March 24, 2026, from Trian Partners AM Holdco II, Ltd., Jupiter Core Holdings, L.P., Jupiter AM Investors, L.P., Trian Partners AM Fund, L.P. and Trian Partners AM Parallel Fund, L.P., in favor of Janus Henderson Group plc.⸸

(f) None.

(g) None.

107 Filing Fee Table.

⸸ Certain information in this exhibit has been redacted and filed separately with the Securities and Exchange Commission, and confidential treatment has been requested with respect to such omitted information.

+ Previously filed with the Transaction Statement on Schedule 13E-3 filed with the SEC on January 30, 2026.

++ Previously filed with Amendment No. 2 to the Transaction Statement on Schedule 13E-3 filed with the SEC on March 11, 2026.

SIGNATURES

After due inquiry and to the best of the undersigned’s knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

[Signature Page to SC 13E-3]

After due inquiry and to the best of the undersigned’s knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

[Signature Page to SC 13E-3]

[Signature Page to SC 13E-3]