Allen & Overy (A&O), Travers Smith and Ashurst have all picked up roles on the biggest buyout in the UK for more than a year.

Apax is set to purchase pharmaceutical support company Marken for a reported £975m from Intermediate Capital Group (ICG), with the deal expected to close in early 2010.

Apax is being advised by A&O, with private equity partners Derek Baird and Gordon Milne leading the magic circle firm's team. Ashurst has taken a role advising the private equity house on competition issues, fielding a team led by Brussels-based partner Julian Ellison.

Travers is advising ICG, with corporate head Chris Hale and private equity partner Helen Croke at the helm. The City outfit is also advising ICG management on the equity arrangements with Apax, with the company expected to retain a stake in Marken.

ICG also instructed Ashurst on the deal, with corporate partner Jonathan Angell leading the firm's team.

Travers' Hale (pictured) commented: "The private equity deal market has been showing signs of life for the last two or three months. This transaction provides considerable optimism for this part of the M&A world for the next few months. It is the largest private equity deal for over a year. We are naturally pleased to have played the leading legal role on it."

Both A&O and Ashurst took key roles on one of the largest leveraged buyouts this year, when the firms advised on Charterhouse Capital Partners' £553m buyout of Candover-owned energy consultancy Wood Mackenzie in June.