White Mountains Insurance Group Ltd, the Bermudian-domiciled financial services holding company, has signed a definitive agreement to sell NSM Insurance Group to investment funds affiliated with global investment firm Carlyle in a transaction that values NSM at $1.775 billion.

White Mountains said it expected the transaction would result in a gain of approximately $280 to its adjusted book value per share and would increase undeployed capital from approximately $0.4 billion to approximately $1.7 billion.

The transaction is expected to close during the second half of 2022.

The closing is subject to regulatory approvals and other customary closing conditions, but is not subject to a financing condition.

White Mountains said it would file a current report on Form 8-K with the US Securities and Exchange Commission containing a summary of terms and conditions of the proposed transaction.

"The NSM team has done a tremendous job building a market-leading specialty insurance distribution platform. It has been our pleasure to partner with them along the way," said Manning Rountree, chief executive officer of White Mountains.

"This transaction is a win for both White Mountains shareholders and NSM management and employees. We want to thank Geof, Bill, Marc, Jonathan and the entire NSM team for all of their hard work. NSM is well positioned going forward, and we wish them continued success."

Geof McKernan, chief executive officer of NSM, said: "We thank Manning, Morgan, Chris and the rest of the White Mountains team for their valuable contributions and support throughout our partnership.

"Together, we achieved strong organic growth, completed six strategic acquisitions, added high-quality talent and built a specialised, diversified and scaled insurance distribution platform. We could not be happier with this outcome and are excited to partner with Carlyle as we embark on NSM's next stage of growth."