James will join Mofo as a partner in November to establish a tax practice in London. He has close links with the San Francisco firm, having worked with Mofo's corporate team on a number of deals.
"This rounds out our corporate practice," said Mofo London managing partner Julian Thurston. "Our mission is to grow sensibly in London to about 70-100 full-time lawyers. Then you can sustain a trainee programme and grow organically. There's only a future for US firms if a goodly percentage of work is sourced locally."
James is Mofo's seventh partner hire in nine months. The firm hired a three-partner outsourcing team from Shaw Pittman and recently boosted the corporate practice with three new partners.
A Bird & Bird spokesperson said: "Trevor has contributed a lot to the development of the London and international tax practices. We wish him well. Of course, we continue to build our tax practice."