For Shareholders

HAMILTON, Bermuda, Aug 26, 2010 /PRNewswire via COMTEX/ -- White Mountains Insurance Group, Ltd. (NYSE: WTM) announced today that its Board of Directors authorised the Company to repurchase up to an additional 600,000 common shares, from time to time, subject to market conditions. This authorisation is in addition to the Company's existing 1 million share authorization. As of July 31, 2010, the Company had repurchased roughly 840,000 common shares under the original authorization approved in August 2006.

White Mountains Chairman and CEO Ray Barrette stated, "We continue to pursue many value enhancing opportunities, but at current prices we believe buying back shares is the best use of our undeployed capital for now."

Shares may be purchased in the open market, through privately negotiated transactions or otherwise. The timing and actual number of shares repurchased will depend on a variety of factors, including stock price, alternative opportunities and other market conditions. The repurchase authorisation does not obligate White Mountains to acquire any specific number of shares.

The Company intends to fund any repurchases with available cash.

ADDITIONAL INFORMATION

White Mountains is a Bermuda-domiciled financial services holding company traded on the New York Stock Exchange and the Bermuda Stock Exchange under the symbol WTM. Additional financial information and other items of interest are available at the Company's web site located at http://www.whitemountains.com/.

Safe Harbor Statement under the Private Securities Litigation Reform Act of 1995

This press release 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 release which address activities, events or developments which we expect or anticipate will or may occur in the future are forward-looking statements. The words "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':

    X      changes in adjusted book value per share or return on equity;
    X      business strategy;
    X      financial and operating targets or plans;
            incurred losses and the adequacy of its loss and loss adjustment
    X       expense reserves and related reinsurance;
            projections of revenues, income (or loss), earnings (or loss) per
    X       share, dividends, market share or other financial forecasts;
    X      expansion and growth of our business and operations; and
    X      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 our expectations and predictions is subject to a number of risks and uncertainties that could cause actual results to differ materially from expectations, including:

            the risks associated with Item 1A of White Mountains' 2009
    X       Annual Report on Form 10-K;
            claims arising from catastrophic events, such as hurricanes,
    X       earthquakes, floods or terrorist attacks;
    X      the continued availability of capital and financing;
    X      general economic, market or business conditions;
            business opportunities (or lack thereof) that may be presented
    X       to it and pursued;
            competitive forces, including the conduct of other property and
    X       casualty insurers and reinsurers;
            changes in domestic or foreign laws or regulations, or their
            interpretation, applicable to White Mountains, its competitors
    X       or its clients;
            an economic downturn or other economic conditions adversely
    X       affecting its financial position;
            recorded loss reserves subsequently proving to have been
    X       inadequate;
            actions taken by ratings agencies from time to time, such as
            financial strength or credit ratings downgrades or placing
    X       ratings on negative watch;
            other factors, most of which are beyond White Mountains'
    X       control.

Consequently, all of the forward-looking statements made in this press release 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.

CONTACT: David Foy

Tel: (203) 458-5850

SOURCE White Mountains Insurance Group, Ltd.