Greg Coffey, the high-profile fund manager at New York-listed GLG Partners will have to give up about $250 million's worth of shares in order to leave the London-based hedge fund and start his own fund, according to the Financial Times. Mr Coffey will stay at the company until October as part of a hastily worked out arrangement following his unexpected resignation. His resignation has hit GLG's shares. The controversy about his departure underscores how the moves of star managers can have a major and adverse impact on a company if they leave. The departure of Mr Coffey, an Australian who runs $7 billion of GLG’s $25 billion funds under management, is a serious blow to GLG as his investors may choose to go with him. Mr Coffey was the best-performing manager at GLG and one of the top performing hedge fund managers in the world in the past two years. His GLG Emerging Markets fund was up almost 51 per cent last year and 60 per cent the year before.