PRESS RELEASE -

HAMILTON, Bermuda, December 8, 2025 /PRNewswire/ -- White Mountains Insurance Group, Ltd. (NYSE: WTM) (“White Mountains”) announced today that it has completed the sale of a controlling interest in Bamboo to affiliates of funds advised by CVC Capital Partners (“CVC”). White Mountains continues to retain an approximately 15% fully-diluted equity stake in Bamboo.

Contact:

Rob Seelig

+1 (603) 640-2212

ir@whitemountains.com

The unaudited pro forma condensed consolidated financial statements (the “Pro Forma Financial Statements”) present pro forma adjustments that reflect the impact of the Bamboo Sale Transaction. The Pro Forma Financial Statements give effect to the Bamboo Sale Transaction and related adjustments in accordance with Article 11 of the Securities and Exchange Commission’s Regulation S-X. The unaudited pro forma condensed consolidated balance sheet as of September 30, 2025 gives effect to the Bamboo Sale Transaction assuming it closed on September 30, 2025. The unaudited pro forma condensed consolidated statements of operations for the nine months ended September 30, 2025 and the year ended December 31, 2024 give effect to the Bamboo Sale Transaction assuming it closed on January 2, 2024, which is the date of White Mountains’s acquisition of the Bamboo Group. The Pro Forma Financial Statements should be read in conjunction with White Mountains’s 2024 Annual Report on Form 10-K and White Mountains’s Quarterly Report on Form 10-Q for the period ended September 30, 2025.

The Pro Forma Financial Statements (i) are presented based on available information and assumptions that management believes are reasonable in order to give effect, on a pro forma basis, to the Bamboo Sale Transaction, (ii) are intended for informational purposes only and (iii) are not intended to reflect the results of operations or the financial position of White Mountains that would have resulted had the Bamboo Sale Transaction been completed as of and during the periods presented or the results that may be obtained by White Mountains in the future. The Pro Forma Financial Statements as of and for the periods presented do not reflect future events that are not directly attributable to the Bamboo Sale Transaction and that may occur after the Bamboo Sale Transaction. Future results may vary significantly from the results reflected in the Pro Forma Financial Statements.

White Mountains presents its consolidated financial statements using the conglomerate view that presents each segment separately. For purposes of the Pro Forma Financial Statements, White Mountains has condensed the information related to segments that are not impacted by the Bamboo Sale Transaction.

(1) Adjustment to reflect White Mountains’s estimated net cash proceeds assuming the Bamboo Sale Transaction closed on September 30, 2025. The following table presents the calculation of net cash proceeds to White Mountains:

(a) Includes $13.4 of unrecognized equity-based compensation to be recognized in connection with the Bamboo Sale Transaction assuming it closed on September 30, 2025.

(b) Includes $2.7 of transaction expenses that were accrued in White Mountains’s historical financial statements.

(c) Includes $3.6 held in escrow that is expected to be released in the first half of 2026.

(2) Adjustment to reflect the sale of the Bamboo Group’s assets and liabilities assuming the Bamboo Sale Transaction closed on September 30, 2025.

(3) Adjustment to reflect the estimated incremental costs related to White Mountains’s incentive compensation plans assuming the Bamboo Sale Transaction closed on September 30, 2025. The adjustment excludes $28.0 million of estimated incremental costs related to White Mountains’s incentive compensation plans that were accrued in White Mountains’s historical financial statements. The estimated costs are driven primarily by the increase in the estimated harvest percentages reflecting the impact of the Bamboo Sale Transaction.

(4) Adjustment to reflect White Mountains’s estimated net transaction gain, after tax, assuming the Bamboo Sale Transaction closed on September 30, 2025. The following table presents the calculation of White Mountains’s estimated net transaction gain, after tax, and the increase in book value as of September 30, 2025:

(a) Adjustment to reflect the total estimated incremental costs of $33.0 related to White Mountains’s incentive compensation plans assuming the Bamboo Sale Transaction closed on September 30, 2025, including $28.0 of costs that were accrued in White Mountains’s historical financial statements. See Note (3) above.

(5) Adjustment to remove noncontrolling interests related to the Bamboo Group assuming the Bamboo Sale Transaction closed on September 30, 2025.

(6) Adjustment to remove the Bamboo Group’s results of operations assuming the Bamboo Sale Transaction closed on January 2, 2024, which is the date of White Mountains’s acquisition of the Bamboo Group.

(7) Adjustment to remove $28.0 million of incentive compensation expenses and $2.0 million of transaction expenses that were accrued in White Mountains’s historical financial statements. For purposes of the Pro Forma Financial Statements, these amounts were recognized in the pro forma condensed consolidated statement of operations for the year ended December 31, 2024 assuming the Bamboo Sale Transaction closed on January 2, 2024.

(8)    Adjustment to reflect White Mountains’s estimated net transaction gain, after tax, assuming the Bamboo Sale Transaction closed on January 2, 2024. See Note (4) for the calculation of the net transaction gain, after tax.

(9)    Adjustment to reflect the estimated incremental costs related to White Mountains’s incentive compensation plans assuming the Bamboo Sale Transaction closed on January 2, 2024.

These Pro Forma Financial Statements may contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. All statements, other than statements of historical facts, included or referenced in this filing which address activities, events or developments which White Mountains expects or anticipates will or may occur in the future are forward-looking statements. The words “could”, “will”, “believe”, “intend”, “expect”, “anticipate”, “project”, “estimate”, “predict” and similar expressions are also intended to identify forward-looking statements. These forward-looking statements include, among others, statements with respect to White Mountains’s:

▪change in book value per share or return on equity;

▪business strategy;

▪financial and operating targets or plans;

▪incurred loss and LAE and the adequacy of its loss and LAE reserves and related reinsurance;

▪projections of revenues, income (or loss), earnings (or loss) per share, EBITDA, adjusted EBITDA, dividends, market share or other financial forecasts of White Mountains or its businesses;

▪expansion and growth of its business and operations; and

▪future capital expenditures.

These statements are based on certain assumptions and analyses made by White Mountains in light of its experience and perception of historical trends, current conditions and expected future developments, as well as other factors believed to be appropriate in the circumstances. However, whether actual results and developments will conform to its expectations and predictions is subject to risks and uncertainties that could cause actual results to differ materially from expectations, including:

▪the risks that are described from time to time in White Mountains’s filings with the Securities and Exchange Commission, including but not limited to White Mountains’s 2024 Annual Report on Form 10-K;

▪whether the potential benefits of any transaction, including the Transaction, will be realized;

▪claims arising from catastrophic events, such as hurricanes, windstorms, earthquakes, floods, wildfires, tornados, tsunamis, severe weather, public health crises, terrorist attacks, was and war-like actions, explosions, infrastructure failures or cyber-attacks;

▪recorded loss reserves subsequently proving to have been inadequate;

▪the market value of White Mountains’s investment in MediaAlpha;

▪business opportunities (or lack thereof) that may be presented to it and pursued;

▪actions taken by rating agencies, such as financial strength or credit ratings downgrades or placing ratings on negative watch;

▪the continued availability of capital and financing;

▪the continued availability of fronting and reinsurance capacity;

▪deterioration of general economic, market or business conditions, including due to outbreaks of contagious disease and corresponding mitigation efforts;

▪competitive forces, including the conduct of other insurers;

▪changes in domestic or foreign laws or regulations, or their interpretation, applicable to White Mountains, its competitors or its customers; and

▪other factors, most of which are beyond White Mountains’s control.

Consequently, all of the forward-looking statements made in these Pro Forma Financial Statements are qualified by these cautionary statements, and there can be no assurance that the actual results or developments anticipated by White Mountains will be realized or, even if substantially realized, that they will have the expected consequences to, or effects on, White Mountains or its business or operations. White Mountains assumes no obligation to publicly update any such forward-looking statements, whether as a result of new information, future events or otherwise.