Chris Gamble, the first female director of the Royal Institute of International Affairs at Chatham House, is to resign just two years after taking the job.
Dr Gamble, who is leaving to spend more time with her unwell husband, has had a turbulent two years, fighting to make the institute solvent and to attract more corporate sponsors and younger members.
She said: "My biggest achievement has been to get financial stability. We no longer drag a deficit behind us when we approach sponsors."
An expert on women in public life, she was reported at one time to be facing a case of sex discrimination from a former male employee. "That was only ever just a rumour," she said.
She also had to launch an inquiry into claims that a member of staff spied for the East German Stasi. "We established that the only documents the Stasi obtained were those open to members, and indeed to members of the press," she said. "The incident showed how central we are to international affairs."
She added: "Our objectivity is one of our greatest assets"