Clifford Chance (CC) and Berwin Leighton Paisner (BLP) have won lead roles on a major City real estate deal which has seen the ownership of Allen & Overy's (A&O) City headquarters change hands.

CC advised Hammerson and Oman Investment Fund (OIF) on the deal, which saw the pair sell their 25:75 joint venture – whose principal asset is the long leasehold interest in the Bishops Square offices in London's Spitalfields – to JP Morgan Asset Management.

The deal saw the Bishops Square property – of which A&O rents 71,900 sq m of office space – valued at £557m.

BLP advised two funds of JP Morgan Asset Management on the purchase of the assets, which saw Hammerson take net proceeds of £79m. Deloitte also advised JP Morgan Asset Management's funds, while Jones Lang LaSalle advised the sellers on the deal.

Hammerson sold a 75% stake to OIF in June 2009 and accounted for its 25% interest as an associate, with CC advising Hammerson on the deal while DLA Piper advised OIF.

CC London real estate head Jonathan Solomon is a longstanding adviser to Hammerson and has advised on the Bishops Square development for 15 years. He started the work while a partner at Norton Rose and brought it with him when he joined CC in 2000.

It is understood that JP Morgan Asset Management is a relatively new client of BLP, with Linklaters having previously taken major roles for the investor.

Addleshaw Goddard also won a role on the deal, advising a syndicate of banks led by Bayerische Landesbank, which provided the funding for the deal, with a team led by head of real estate finance Paul Salsbury and legal director Rhodri Davies.