Stephen Hill, chief executive of Betfair, resigned on Friday but will keep more than 3m shares in the internet betting exchange that could be worth as much as £30m when the group floats.
Betfair's profits have risen six-fold during Mr Hill's two years with Betfair, while its turnover has increased four-fold.
His resignation came as the company confirmed it had postponed plans for an IPO.
The group's leading shareholders are known to be keen to secure a £750m-£1bn valuation for the business when it floats, which will probably be after next year's football World Cup.
“I have enjoyed my time at Betfair and I believe I have done what I set out to do,” Mr Hill said. “The business is thriving; international expansion is progressing well; and our portfolio of products is growing. However, I feel the time is right to move on.”
Mr Hill, a former chief executive of the Financial Times, plans to set up a fund which would invest in underperforming small and medium sized companies.
Sir Robert Horton, Betfair's chairman, said: “Stephen leaves us with a top-class management team and the ability to scale significantly. We understand his reasons for leaving and wish him all the best in his new venture.”
He joined Betfair in 2003 after an abortive attempt at buying the FT's portfolio of business magazines. A keen triathlete, he studied law at Cambridge before joining Boston Consulting. A stint at Guinness followed, before Mr Hill moved on to Pearson, the media group that owns the FT.
Mr Hill will leave Betfair with 3.125m shares. The shares were put into a trust this year with a valuation believed to be 271p each, giving them a current value of more than £8m. This would rise to £30m if the group secured a £1bn valuation at float.
Betting exchanges have revolutionised the gambling industry because they allow punters to bet against each other without having to use a bookmaker.
Betfair has grown rapidly but has stuttered this year after failing to gain a licence to operate in Australia. However, the group has gained operating licences in Malta, Austria and Germany and is hopeful that the World Cup next year will be a betting bonanza.
The group has also hinted that it may quit Britain, where it is based, if the Treasury moves to change the tax regime for betting exchanges.
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