Tim Cook might be the most powerful man you've never heard of. Since Steve Jobs stepped down as chief executive of Apple because of failing health, his protégé has taken the helm at 1 Infinite Loop, Cupertino, California. The soft-spoken 50-year-old inherits the world's most valuable technology company, with more cash than the US Treasury ($76.4bn v $73.7bn). Like his mentor - who poached him from Compaq in 1998 - Cook is a workaholic. He has been known to hold "pre-meetings" on Sunday evenings ready for the week ahead. While Cook might now be in control of a company at the peak of its power, his challenge is to prove he can retain the "visionary" tag so often applied to Jobs, champion of iPods, iPhones and iPads. With the release of the iPhone 5 imminent, it's time to make his mark.
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