Addleshaw Goddard and Allen & Overy (A&O) have scooped roles on the UK's largest-ever building society merger, with total asset values of more than £150bn and 13-million-plus members.
The merger of Nationwide Building Society and smaller rival Portman Building Society is subject to approval by the Office of Fair Trading, Portman members and the Financial Services Authority, but is expected to become effective by September 2007.
Alistair Asher, head of A&O's financial institutions group, said: "This is the number-one building society merging with the number three and it will make smaller building societies question what their meaning in life is.
"If you have a building society that's committed to being a building society but with these efficiencies of scale, it will be hard for them to compete."
The merger is expected to create the UK's second-largest mortgage lender and the second-largest retail savings provider. The society will take the Nationwide name.
A&O is advising longstanding client Nationwide, led by Asher and fellow London-based corporate partners Richard Slynn and Asher. The firm has advised Nationwide on corporate transactions for more than 10 years.
Addleshaws is advising Portman, led by London-based corporate partners Adam Bennett and Ian McIntosh.
Bennett has advised Portman for 15 years. His work for Portman has included advising the society on its £95m acquisition of Sun Bank in 2001.
Bennett has also advised on numerous other recent building society tie-ups, including Newcastle-based Universal Building Society's merger with Newcastle Building Society, which is due to complete in December, and the merger of the Mercantile Building Society with Leeds Building Society, which completed in August.