Ashurst is set to advise on the £9.4bn approach for BAA by a Goldman Sachs-led consortium, Legal Week has learned, in one of the firm's biggest mandates of recent years.

The top 10 London firm is lined up as a senior adviser to the consortium, which last month made an unsolicited bid for the FTSE 100 airports operator.

BAA, which is currently attempting to fend off a rival bid from Spanish construction giant Ferrovial, made the approach public earlier this month (16 April) after it announced that it had rejected the offer from the Goldman consortium.

It is currently unclear whether Goldman intends to return with a revised offer, though its consortium was last week (18 April) reported to have attracted support from US insurance giant AIG and interest from General Electric. A return bid would land Ashurst its most notable corporate instruction since it was instructed by Philip Green on a failed £9bn approach for Marks & Spencer in 2004, a role it gained through a Freshfields Bruckhaus Deringer conflict.

Milbank Tweed Hadley & McCloy London corporate partner Tim Emmerson and associate Suhrud Mehta are also in line to advise the debt providers to the Goldman consortium. Emmerson has strong links with Goldman and has advised the investment bank on a number of deals in recent months, including approaches for ITV.

News of the Goldman bid comes as Ferrovial gears up to make another approach for BAA, which holds among its assets Heathrow, Gatwick and Stansted.

BAA is being advised by Herbert Smith corporate partner Gareth Roberts and on debt finance issues by Allen & Overy partner Boyan Wells. Freshfields is lead counsel to the Ferrovial consortium.

Ashurst declined to comment. First reported on legalweek.com (18 April).