Freshfields has recruited Eric Schwartz, former secretary general of the ICC International Court of Arbitration, from Paris-based rival Salans Hertzfeld & Heilbronn.
Schwartz has acted as arbitrator or counsel in international arbitrations from Asia and Africa to the Americas and is a leading light in his profession.
Jan Paulsson, the head of Freshfields' international arbitration group, said he was delighted Schwartz had accepted the open invitation he had left with him two years ago.
"We were at Yale together in the 1970s. There were a number of promising young lawyers there at the time including Bill Clinton, Hillary Rodham and Clarence Thomas. If I had to choose one who would give measured, analytical advice to our clients, I think I would pick Eric."
Schwartz said he had wanted to "give it a go" at Salans because of the friends he had there, but said Freshfields' status as a premier international arbitration firm and its global support structure meant "it was a marriage that made sense".
"The conclusion I have come to after a couple of years is that Freshfields will be better for my practice."
Salans partner Sarah Francois-Poncet said the firm was disappointed to lose Schwartz, but there was no bad feeling.
"I think it's more to do with security than happiness. He will be more comfortable in a place that's less entrepreneurial." He is taking a couple of his cases with him and a couple will be staying, she said.