OneBeacon Expands Personal Insurance Line with OneChoice

Company Leveraging the Web to Deliver Comprehensive Protection Quickly, Accurately

BOSTON, May 16 -- With its suite of OneChoice auto, homeowners and package products, OneBeacon Insurance delivers comprehensive protection to fit the needs and lifestyles of a broad range of drivers and property owners throughout the Northeast. OneBeacon introduced its new auto product in 2004 and is launching new homeowners and package products during 2005.

OneBeacon currently offers OneChoice Auto in Connecticut, Maine, New Hampshire, New York and Rhode Island, and OneChoice Homeowners in Maine, New York and New Jersey. Consumers in New York can combine auto, home, boat and umbrella coverage with OneChoice Package, which helps eliminate gaps in protection and provides the convenience of one bill.

"We've expanded our approach to personal insurance significantly," said Alex Archimedes, head of Personal Lines at OneBeacon, "and our multi-tiered products now enable us to offer insurance solutions for most drivers and most vehicles. We can also help more property owners protect their dwellings and personal possessions, and meet their liability needs."

OneChoice platform quick, easy to use

Agencies can process new policies through state-of-the-art Web-based technology that puts high levels of service at their fingertips. Designed as a one-touch application, the OneChoice platform contains imbedded underwriting rules and real-time quoting so agents can quickly submit business and return to their sales and marketing activities. It also allows producers to issue policies immediately and support all policy life cycle transactions over the Internet.

In addition to the OneChoice system, OneBeacon's partners can take advantage of electronic capabilities to access billing information, submit claims and monitor their status, track agency loss results, manage access for individual producers, and more.

"It's all part of our commitment to providing the tools, support and convenience that enhance agents' productivity," said Archimedes.

Headquartered in Boston, Massachusetts, OneBeacon Insurance Group offers a wide range of specialty, personal and commercial insurance products and services sold primarily through select independent agents. OneBeacon is one of the oldest property and casualty insurers in the United States, tracing its roots to 1831 and the Potomac Fire Insurance Company. The company's specialty businesses provide customized coverages to certain niche markets including ocean marine, professional liability and agribusiness, among others. OneBeacon serves personal insurance customers and small to midsized businesses through a variety of highly segmented products.

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 and the Bermuda Stock Exchange under the symbol "WTM."

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

The information contained in this earnings 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':

   -- 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 our 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 our expectations and predictions is subject to a number of risks and uncertainties that could cause actual results to differ materially from expectations, including:

   -- claims arising from catastrophic events, such as hurricanes,
      earthquakes, floods or terrorist attacks;
   -- 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 earnings 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.