Banking specialist Ian Coles has been appointed "partner-in-charge" of Mayer Brown & Platt's London office.
He is believed to be only the second non-American partner to head the London office of a US firm.
Coles was one of the first British lawyers to work for a US law firm when he joined Mayer Brown & Platt's New York office in 1981.
He moved to London in 1984 and became a partner in 1987, specialising in banking and international project finance.
Coles says his appointment reflects the firm's recent decision to hire more local partners and to "get a more English culture about the place".
He adds that Mayer Brown & Platt aims to double the size of its London office of 30 lawyers over the next year.
Coles took up his post on 1 January. He replaces Richard Cole, who held the post for 10 years and remains a senior partner with the firm.
This year marks the 25th anniversary of the opening of the firm's London office.