Clifford Chance has won the work on a £25bn Spanish bank merger, which it regards as a breakthrough deal resulting from its merger with Rogers & Wells.
Merrill Lynch has appointed both Clifford Chance's Madrid office and Rogers & Wells to advise on the merger of Banco Bilbao Vizcaya (BBV) with Argentaria, Spain's second and third largest banks respectively.
Clifford Chance believes the mega deal is a turning point because pre-merger the UK firm would never have won the lucrative work to put the US side of the deal together.
That work is now going to Rogers & Wells' New York office.
Merrill Lynch is financial adviser for both sides of the friendly merger.
Spanish firm Uria Menendez has been appointed as legal adviser by BBV and Argentaria but was not prepared to comment on the deal.
The merger of the two banks will create the second largest bank in the European single currency zone, worth euro37.7bn (£25.1bn).
A large percentage of shares for both banks are held in the New York stock exchange, so the deal needed a US law input.
Securities partner Inigo Gomez-Jordona and Maria Jose Menendez are working on the deal in the Clifford Chance Madrid office while Bob King is heading the Rogers & Wells New York team.
King will become the new global head of securities when Clifford Chance and Rogers & Wells merge in the new year.
"This deal turned out to be exactly the sort of thing that we have been telling clients about in the lead up to the merger. When a transaction goes global we can make use of our global coverage for them," says King.
"Merrill Lynch had a deal to do that it thought was Spain driven and orientated and it was looking at Clifford Chance in Madrid to handle that. Then it discovered a sizeable US aspect in the shareholders in the US.
"It really needed US counsel so Clifford Chance asked whether it would like to use Rogers & Wells."
BBV is in talks with Italian bank Unicredito SpA regarding a share swap and joint venture that is rumoured to be the precursor to a merger.
For both Clifford Chance and Rogers & Wells, Merrill Lynch is a major client, and for the US firm it is believed to be the sole reason for maintaining its London office.