The 20-partner firm has set a June deadline for establishing a small City presence, to be jointly funded with its two new allies.
Gomez-Acebo's new allies are 45-lawyer Lisbon firm Viera de Almeida and Brazil's biggest firm Pinhero Neto. The three firms have agreed to a formal and exclusive alliance with each other.
The London base will serve mainly as liaison office and will be staffed by just one Spanish partner, working along side a team of associates who will work there for rotational six-month terms.
Once the UK practice is up and running, jointly-funded offices in New York and Brussels will be next on the agenda.
Gomez-Acebo is also said to be in negotiations with an Argentinean firm with a view to including it in its new alliance