Kirkland & Ellis London head Jim Learner is set to leave the firm this summer to take up a role at a US private equity house.

Learner, who was involved in launching the US firm's London office in 1994 and is now responsible for all European operations, announced his forthcoming departure to staff earlier this week.

He told partners he intended to return to the US at the end of the summer for personal reasons and is broadly expected to be joining a buyout house, although it is unclear which one. At Kirkland his main client is Bain Capital, although he also works with houses including Apax Partners, Apollo Management and Towerbrook Capital Partners.

His departure will leave a vacancy on the firm's board, with London partners expecting the Chicago firm to appoint another City partner to replace him.

One partner commented: "Officially there are no management roles in London, but there will be one London-based partner with board responsibilities. Obviously this partner will also have management responsibilities in London."

Another commented: "This is a real loss for the firm – Jim has been a figurehead in London since the launch. The departure will enable other firm such as Ropes & Gray to move in on the Bain relationship."

Learner has been heavily involved in Kirkland's London expansion, with the firm's office in the Gherkin now housing around 100 lawyers, including a number of high-profile partners lured from City such as SJ Berwin, Linklaters and Allen & Overy.