Cancellation and Termination of Existing Credit Facility In connection with the completion of the Merger, the Company issued a notice, dated June 25, 2026, to cancel and terminate, effective as of the Closing Date, the revolving credit facility agreement, dated as of June 30, 2023 (as amended, supplemented or otherwise modified from time to time, the “ Revolving Credit Facility Agreement ”), by and between the Company and Bank of America Europe Designated Activity Company, as facility agent.…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth in the Introductory Note and

As a result of the consummation of the Merger, at the Effective Time, a change in control of the Company occurred and the Company became a wholly owned subsidiary of Parent. The aggregate Merger Consideration payable by Parent in connection with the Merger is approximately $6.5 billion, funded by a combination of cash provided by an investor group led by Trian Fund Management, L.P. and General Catalyst Group Management, LLC, as well as preferred equity financing that has been provided by Mass…

On the Closing Date, the Company notified the New York Stock Exchange (“ NYSE ”) of the consummation of the Merger and that each outstanding Share had been converted into the right to receive the Merger Consideration (except for Shares held by Parent and as otherwise provided in the Amended Merger Agreement). The Company requested that the NYSE (i) halt trading of the Shares on the NYSE prior to the opening of trading on July 1, 2026, which is the day immediately following the Closing Date, (…

As a result of the consummation of the Merger, at the Effective Time, holders of Shares immediately prior to such time ceased to have any rights as shareholders of the Company (other than their right to receive Merger Consideration (except for Shares held by Parent and as otherwise provided in the Amended Merger Agreement) pursuant to the terms of the Amended Merger Agreement).

Pursuant to the Amended Merger Agreement, each ordinary share, par value $1.50 per share, of the Company (collectively, the “ Shares ”) issued and outstanding immediately prior to the effective time of the Merger (the “ Effective Time ”) (except for Shares held by Parent and as otherwise provided in the Amended Merger Agreement) was converted into the right to receive $52.00 per Share in cash, without interest (the “ Merger Consideration ”). Also at the Effective Time: · each (i) outstanding…

Directors and officers transitioned due to a merger.

On the Closing Date, concurrently with the closing of the Merger, the Surviving Company, as holdings, and Janus Henderson US (Holdings) Inc. (as survivor of the merger among Jupiter Borrower, Inc. and Janus Henderson US (Holdings) Inc.), as the parent borrower, entered into that certain Credit Agreement with JPMorgan Chase Bank, N.A., as administrative agent and collateral agent, the lenders from time to time party thereto and the subsidiary borrowers from time to time party thereto (the “ Cr…

Entry into a Material Definitive Agreement. Amendment to Agreement and Plan of Merger On June 16, 2026, the Company entered into a side letter agreement (the “ Side Letter ”) with Parent and Merger Sub, which further supplements and amends certain terms of the Merger Agreement (as further amended and supplemented by the Side Letter, the “ Amended Merger Agreement ”). Pursuant to the terms of the Side Letter, the Company, Parent and Merger Sub have agreed that, among other things: i. the closi…

Results of Operations and Financial Condition. On May 8, 2026, Janus Henderson Group plc issued a press release reporting its financial results for the first quarter 2026. A copy of that press release is being furnished as Exhibit 99.1 to this Current Report.

and Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “ Exchange Act ”) or otherwise subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except as set forth by specific reference in such filing. Forward Looking Statements Certain statements in this Form 8-K not based on h…

Other Events. On March 24, 2026, the Company issued a press release announcing the signing of the Amendment. A copy of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. Forward Looking Statements Certain statements in this Form 8-K not based on historical facts are “forward-looking statements” within the meaning of the federal securities laws. Such forward-looking statements involve known and unknown risks and uncertainti…

Entry into a Material Definitive Agreement. Amendment to Agreement and Plan of Merger On March 24, 2026, Janus Henderson Group plc (the “ Company ”), entered into Amendment No. 1 to the Agreement and Plan of Merger (the “ Amendment ”) with Jupiter Company Limited, a company incorporated in Jersey (“ Parent ”), and Jupiter Merger Sub Limited, a company incorporated in Jersey and a wholly owned subsidiary of Parent (“ Merger Sub ”), which amends the previously announced Agreement and Plan of Me…

Results of Operations and Financial Condition. On January 30, 2026, Janus Henderson Group plc issued a press release reporting its financial results for the fourth quarter and full-year 2025. A copy of that press release is being furnished as Exhibit 99.1 to this Current Report.

Other Events On December 22, 2025, the Company issued a press release announcing its entry into the Merger Agreement. A copy of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. Forward Looking Statements Certain statements in this Form 8-K not based on historical facts are “forward-looking statements” within the meaning of the federal securities laws, including Section 21E of the Securities Exchange Act of 1934, as amend…

Entry into a Material Definitive Agreement. Agreement and Plan of Merger On December 21, 2025, Janus Henderson Group plc (the “ Company ”), Jupiter Company Limited, a company incorporated in Jersey (“ Parent ”), and Jupiter Merger Sub Limited, a company incorporated in Jersey (“ Merger Sub ”), entered into an Agreement and Plan of Merger (the “ Merger Agreement ”) providing for the acquisition of the Company by Parent. The Merger Agreement provides that, among other things, upon the terms and…

Results of Operations and Financial Condition. On October 30, 2025, Janus Henderson Group plc issued a press release reporting its financial results for the third quarter 2025. A copy of that press release is being furnished as Exhibit 99.1 to this Current Report.

CFO — Roger Thompson: The CFO is retiring with a named internal successor (Sukh Grewal) appointed to take over the role, representing an orderly succession rather than a sudden loss of leadership.

Results of Operations and Financial Condition. On July 31, 2025, Janus Henderson Group plc issued a press release reporting its financial results for the second quarter 2025. A copy of that press release is being furnished as Exhibit 99.1 to this Current Report.

Global Chief Operating Officer — James R. Lowry: The Global Chief Operating Officer is departing the company, representing the loss of a senior executive.

CEO — Ali Dibadj: The filing discloses a new employment agreement and compensation package for the current CEO, which is a compensatory arrangement rather than a change in personnel or a departure.

Results of Operations and Financial Condition. On May 1, 2025, Janus Henderson Group plc issued a press release reporting its financial results for the first quarter 2025. A copy of that press release is being furnished as Exhibit 99.1 to this Current Report.

Other Events. On April 8, 2025, the Company issued a press release announcing the strategic partnership with Guardian. A copy of that press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Unregistered Sales of Equity Securities. On April 7, 2025, Janus Henderson Group plc (“JHG” or the “Company”) and The Guardian Life Insurance Company of America (“Guardian”) entered into a definitive transaction agreement (the “Agreement”), pursuant to which, in consideration for certain commercial arrangements between the Company and Guardian, the Company agreed to deliver to Guardian at closing, in a private placement transaction (the “Private Placement”), a warrant (the “Warrant”) to purch…

Results of Operations and Financial Condition. On January 31, 2025, Janus Henderson Group plc issued a press release reporting its financial results for the fourth quarter and full-year 2024. A copy of that press release is being furnished as Exhibit 99.1 to this Current Report.