Reynolds Porter Chamberlain (RPC) and DLA Piper are acting on Grant Thornton's merger with RSM Robson Rhodes in a deal that will create the UK's fifth-largest accounting and business advisory group.

RPC landed the lead role advising Grant Thornton, its first corporate mandate for the client, under corporate partner Tim Anderson and limited liability partnership (LLP) specialist Barry Stimpson.

DLA Piper, which also has a relationship with Grant Thornton, advised Robson Rhodes, with UK corporate head David Raff leading the team.

The deal, which was agreed in principle last week, will place Grant Thornton as the UK's largest accountancy firm outside the 'big four'. The merged firm will have a fee income of approximately £375m and have more than 300 partners operating from 33 locations.

RPC had previously done a lot of work for Grant Thornton on the risk management side of the business and has a good relationship with the client through senior partner Tim Brown and the accountant's liability and risk management adviser, Laurence Kehoe.

Anderson commented: "It is nice to get instructed on the corporate side for this client, as we know them well through their other work. Limited liability partnerships are an interesting animal and there haven't been many large LLP mergers, which makes this deal particularly interesting."

The deal, which was initially agreed last week, is expected to complete on 1 July. The new organisation will continue to be known as Grant Thornton.