Investment bank Merrill Lynch chose Freshfields ahead of Linklaters to advise it on its £3.1bn takeover of Britain's biggest fund manager, Mercury Asset Management (MAM).
The bank's decision to turn to Freshfields for such a major deal has surprised City lawyers, given Linklaters' close association with Merrill Lynch. Linklaters advised on the bank's acquisition of market-making firm Smith New Court in 1995.
A senior corporate finance lawyer at a top five City firm, who did not want to be named, said: "It is clearly a coup. Freshfields had been getting closer to Merrills recently, particularly to its corporate finance people. I suspect the advice as to who to instruct came from them."
Merrills handled its own financial advice work in-house, while MAM used City banker, Lazards.
Linklaters remained good-natured about the situation, with a spokeswoman saying: "Naturally, we are disappointed that Freshfields is handling this particular transaction, but we do have a strong relationship with Merrills, and we are continuing to work with the company on many other projects."
Both firms are regularly instructed by Merrills on many third-party deals, where the bank acts as financial adviser.
Freshfields partner Barry O'Brien led a team comprising 20 lawyers in London, plus lawyers in the Paris, Frankfurt, Madrid, Singapore, Hong Kong, Tokyo and Brussels offices.
Allen & Overy, which advises MAM with Lovell White Durrant and Simmons & Simmons, won the job of advising MAM.
The acquisition will take the total assets managed by Merrill Lynch from $272bn to $449bn.