O'Melveny & Myers is the latest firm to win a role on Grupo Ferrovial's £8bn takeover bid for UK airport owner BAA, joining Freshfields Bruckhaus Deringer, Slaughter and May, Herbert Smith and Canada's Fasken Martineau on the line-up.

Former Ashurst corporate head Chris Ashworth is leading the O'Melveny team advising Singapore's investment company GIC – one of three members of the Ferrovial consortium.

The transaction is the first significant public deal Ashworth has acted on since he joined the US firm in December.

The Ferrovial consortium, which comprises Canada's Caisse de Depot et placement du Quebec and GIC in addition to Ferrovial, now has until 24 April to make a formal offer for BAA after BAA was granted a 'put up or shut up' ruling by the UK Takeover Panel last week.

Ashworth told Legal Week: "It is great to be involved in such a major UK takeover at such an early stage. O'Melveny has worked with GIC before but until I arrived it did not have the capacity in London for a big takeover."

Tax partner Jan Birtwell, corporate of counsel Matt Rees and Eilean Couper and associate James Mulholland are all working with Ashworth at O'Melveny.

Freshfields is leading the advice for Ferrovial and the overall consortium with corporate partners Will Lawes and Patrick Gaynor thought to be advising.

Caisse de Depot et placement du Quebec is being advised by Fasken Martineau corporate partners Daniel Picotte (Montreal) and James Lisson (London). Slaughters corporate partner David Johnson, assisted by associate Marek Petecki, is advising Citigroup as financial adviser to the consortium.

Herbert Smith corporate partner Gareth Roberts is leading the team advising BAA. The firm has previously advised BAA on deals including the £800m sale of a chunk of its property portfolio to insurance group Aviva. Clifford Chance is acting for Citigroup, Royal Bank of Scotland and Banco Santander Central Hispano on its role as lender to the consortium. A team from Allen & Overy, led by capital markets partner Boyan Wells, is advising BAA on a £2bn bond issue that could affect the potential takeover.