White Mountains Completes Reorganization and Rebranding of Reinsurance Business

Hamilton, Bermuda – 13 October, 2011 – In an filing with the Bermuda Stock Exchange dated 12 October, 2011, White Mountains Insurance Group, Ltd. (Tickers: NYSE –  WTM; BSX – WTM.BH) announced the completion of the reorganization and rebranding of its global reinsurance business as the Sirius Group (formerly White Mountains Re).

Allan Waters, President and CEO of Sirius Group, said, "We are pleased to now be operating globally under the longstanding Sirius brand with all our clients benefiting from over $2 billion of regulatory capital. Rating agencies have affirmed our ratings, with AM Best upgrading Sirius America to a group "A", consistent with Sirius International's rating."

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 www.whitemountains.com.

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