OneBeacon Endorsed by Connecticut Retail Merchants Association

Custom Retailers Insurance Available Through Association Benefits Insurance Agency

BOSTON (January 29, 2004) – OneBeacon Insurance Group LLC, a wholly owned subsidiary of White Mountains Insurance Group, Ltd. (NYSE: WTM), today announced that it has been endorsed by the Connecticut Retail Merchants Association (CRMA) as its preferred provider of business-insurance products for CRMA members. This represents the second retail-association endorsement that OneBeacon has received in recent months, both through an exclusive partnership with Association Benefits Insurance Agency, Inc. Last September, the Retailers Association of Massachusetts endorsed OneBeacon and Association Benefits as dedicated insurance providers for its members.

Association Benefits Insurance Agency specializes in risk management solutions for retail associations throughout New England. OneBeacon, a personal and business insurance group, introduced OnePac, a comprehensive small-business owners’ product in 2003. OnePac targets the retail industry with custom insurance coverages and services for over 70 retail classes, which ensures tailor-made protection for Connecticut Retail Merchant Association members. "What a terrific start to the new year," noted Chip Hamann, vice president of commercial lines at OneBeacon.

"We are extremely committed to the retail industry and with this second vote of confidence we look forward to showcasing our capabilities and services to the Connecticut Retail Merchant Association."

Connecticut Retail Merchants Association president Tim Phelan added that "Our Association prides itself on continually enhancing its member services. OnePac, backed by the financial strength of OneBeacon’s A rating, brings our members the peace of mind insurance was originally intended to guarantee. The addition of this terrific product is yet another example of the added value of membership in CRMA. Retailers of all sizes can benefit from our endorsement One Beacon and we are thrilled to join forces with them and ABI."

Association Benefits principal, Frank Michaud added, “We’ve provided many OnePac solutions to our Massachusetts constituents, and it has been very well received. Connecticut is a terrific market that we are thrilled to participate in, so we look forward to making that happen in 2004." Headquartered in Boston, Massachusetts, OneBeacon Insurance Group provides property-casualty and select specialty insurance solutions. With roots dating back 170 years and an A.M. Best rating of A (excellent), OneBeacon’s wide range of personal, commercial and specialty products and services are sold through select property-casualty independent agents.

OneBeacon Insurance Group is wholly owned by White Mountains Insurance Group, Ltd. of Hamilton, Bermuda. White Mountains' principal businesses are conducted through its subsidiaries and affiliates in the business of property-casualty insurance and reinsurance. The company is publicly traded on the New York Stock Exchange under the symbol "WTM."

The Connecticut Retail Merchants Association has been representing retailers at the State Capitol and in the marketplace since 1910. CMRA is the only statewide business group that represents retailers and only retailers. Based in Hartford, its mission is to provide quality service for Connecticut retailers.

Boston-based Association Benefits Insurance was founded in 1991 and provides commercial insurance programs to the members of New England-based Associations.

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

• the continued availability of capital and financing; • general economic, market or business conditions; • business opportunities (or lack thereof) that may be presented to it and pursued; • competitive forces, including the conduct of other property and casualty insurers and reinsurers; • changes in domestic or foreign laws or regulations applicable to White Mountains, its competitors or its clients; • an economic downturn or other economic conditions adversely affecting its financial position; • loss reserves established subsequently proving to have been inadequate; and • other factors, most of which are beyond White Mountains’ 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 update publicly any such forward-looking statements, whether as a result of new information, future events or otherwise.