Investor Group Led by Lightyear Capital to Acquire and Grow Sirius America; New Capital and Executive Additions Position Company for Significant Growth in Program Specialty Insurance; White Mountains Insurance Group Remains a Significant Investor

Business Wire, April 12, 2006

NEW YORK -- Lightyear Capital, LLC ("Lightyear"), a private equity firm focused on financial services, announced today that it is partnering with a highly respected investor group that includes Lehman Brothers Merchant Banking ("Lehman") and AlpInvest Partners ("AlpInvest") to acquire a majority equity stake in Sirius America Insurance Company ("Sirius"), a Delaware domiciled primary underwriter of program specialty insurance, from White Mountains Insurance Group (NYSE: WTM) ("White Mountains"). As part of the transaction, White Mountains will become a member of the investor group by maintaining a significant equity investment in the company, and White Mountains' chief executive officer, Steven Fass, will become a member of the company's board of directors. The transaction, which is subject to customary regulatory and other conditions, is expected to close in the second quarter of 2006.

In addition to the transaction, William Davis, chief executive officer of Sirius, announced today that long time industry veterans Detlef Steiner and Mary Sbaschnig will join the company. Steiner will become chairman of the board of directors and will oversee the execution of the company's strategic and business development plan. Sbaschnig will join the company as a senior executive with responsibilities over administration and information technology.

Program insurance carriers work closely with managing general agents and agents to underwrite specialty classes of primary insurance risk on behalf of insured corporations and properties. The company offers its products through a network of valued agent partners by providing them with best-in-breed technology and training to simplify the pricing, execution and submission of insurance policies in accordance with government regulations, and to allow for superior data collection and integrity needed for underwriting and monitoring such policies. The company also encourages long-term, stable relationships with high quality agent partners and is committed to providing them with unparalleled standards of customer service.

Commenting on the transaction, Donald B. Marron, chairman and chief executive officer of Lightyear, said, "Our investment in Sirius offers Lightyear the opportunity to partner with the most experienced and proven managers in the program insurance industry, and allows us to work closely in a governance capacity with Steve Fass and our friends at Lehman and AlpInvest to oversee an exciting growth plan for the company."

David W. Glenn, managing director of Lightyear added, "The equity sponsors and White Mountains believe the company has the capabilities, executive leadership and capital sponsorship to become the player of choice in the marketplace, and our conviction is evidenced by the quality of our investor group and the additions of Detlef Steiner and Mary Sbaschnig to Bill Davis and his senior management team."

Commenting on the investment, William Davis said, "Sirius America has a well deserved reputation for underwriting success in its business dealings with program managers and reinsurers. With this new partnership between our current supportive owners and additional high quality, reputable investors, along with new senior management members in Detlef and Mary, I believe our company is positioned to become the leader in the marketplace. We are thrilled to enter into a long-term relationship with Lightyear and its co-investors, and that our current owner, White Mountains, is enthusiastically supporting our plans by continuing as a significant investor and partner in this transaction."

ABOUT LIGHTYEAR CAPITAL

Lightyear Capital is a private equity investment firm providing buyout and growth capital to companies in the financial services industry. Based in New York, Lightyear manages approximately $2 billion in assets with investments across the financial services spectrum including brokerage, insurance, leasing, specialty finance, wholesale and consumer banking, and financial technology. Lightyear brings unique strengths and discipline to its investment process, as well as operating, transaction and strategic management experience, along with significant contacts and resources beyond capital. The senior team of professionals has an average of 20 years of financial services-related experience and includes David Glenn, Stewart Gross, Donald Marron (the former Chairman and CEO of PaineWebber Group), Richard Sterne, and Mark Vassallo.

ABOUT LEHMAN BROTHERS MERCHANT BANKING

Lehman Brothers Merchant Banking, part of the Private Equity business of Lehman Brothers (NYSE:LEH), the global investment bank, manages funds that seek significant long-term capital appreciation through direct investments in established operating companies in partnership with management. The group invests in companies with sound business fundamentals, proven operating teams and a compelling business strategy or vision. Lehman Brothers Merchant Banking Partners III L.P. is the Merchant Banking group's current fund. The fund closed successfully in July 2005 with over $1.2 billion of capital commitments from institutions, high net worth individual investors and Lehman Brothers, its affiliates and employees. The group is part of Lehman Brothers Private Equity, which has more than $10 billion of assets under management.