Slaughter and May has bagged its first public work for new client Royal & Sun Alliance (RSA), advising the company on the £158m sale of its US operations and its delisting from the New York Stock Exchange (NYSE).

The magic circle firm was invited to work for RSA in December last year as it had a number of relationships with people inside the FTSE 100 insurance giant. Slaughters is now regarded as RSA's lead corporate counsel.

The appointment will be seen as a blow to both Allen & Overy (A&O) and Ashurst, which had been fighting each other to become the main adviser to the client for a number of years.

Ashurst was historically RSA's primary adviser but the firm loosened its grip on the client when corporate partner Mark Wippell moved to A&O, which subsequently won a number of key instructions.

Slaughters corporate partner Andy Ryde is leading the team advising RSA on winning shareholder approval for the sale of its US operation to Arrowpoint Capital, a vehicle set up by the RSA US management team. The firm is also advising on the UK law aspects of delisting from the NYSE and terminating its SEC registration.

Skadden Arps Slate Meagher & Flom is also advising RSA on the sale with partners Bob Sullivan (insurance), David Friedman (corporate) and Rita Rodin (IP) leading.

Willkie Farr & Gallagher, led by London managing partner Gregory Astrachan, is advising RSA on the US aspects of the delisting and deregistration.