Whitbread, which owns the Marriott hotel chain in the UK, last week revealed that it is attempting to take over Swallow for £578m.
It is the first time that Allen & Overy has acted for Whitbread, whose large deals usually go to Clifford Chance or Slaughter and May.
Brian Wootton, senior corporate partner at Allen & Overy, who is leading a team of six, says: “We have known the company secretary and legal counsel [at Whitbread] for some time.
“We have been trying to persuade them to use us.”
Slaughter and May is conflicted out since it is acting for Swallow.
Clifford Chance advised Whitbread on its failed £2.85bn takeover attempt of Allied Domecq's retail arm earlier this year.
However, Jeremy Brownlow, senior corporate partner at Clifford Chance, who headed a team of 20 on the Allied Domecq deal, refuses to say why the group has gone to Allen & Overy.
In August, Simon Barratt, company secretary and legal affairs director at Whitbread, told The Lawyer that the corporate lawyers for Whitbread were Clifford Chance and Slaughter and May (The Lawyer, 23 August).
According to a Whitbread spokesman, Clifford Chance acted for Barclays Bank and HSBC, which acted as a broker on the deal. He adds: “You don't want too much going through one firm.”
However, he was unable to say whether a conflict of interest had ruled Clifford Chance out from acting as the main legal adviser on the deal.
He says Whitbread got to know Allen & Overy through the banker on the deal, Dresdner Kleinwort Benson, which has worked with the firm in the past.