Microsoft is undeniably a great success story, due to Mr Gates' earlier ability to spot opportunities and devise solutions that he then marketed widely and protected relentlessly. Grasping the immense commercial potential, he licensed, instead of sold outright, the DOS operating system he had developed for IBM. Often ranked as one of 'the greatest business moves of all time', the foresight enabled him to start placing 'a personal computer in every home' in such lucrative and one-sided competition with other companies that he became a multi-billionaire. Also, although he did not invent the graphic user interface allowing users to drag icons and open files on a virtual desktop, he was quick to leverage Windows' market share to proliferate his version, again making Microsoft very rich. The rest, including bundling word-processing, spreadsheet, presentation, e-mail and other 'productivity' applications in Microsoft Office, is history.

Since Microsoft's 1990s golden age, however, the 'creative destruction' in that history has presented Mr Gates with more obstacles than opportunities. He did not see the Internet revolution for what it was - a game-changing phenomenon with adverse implications for Microsoft - until 1995, when it was too late to lead and benefit from the disruption. Its rear-guard action in freezing out the Netscape browser from Windows systems (leading to charges of monopolistic abuse), its continuing but ineffective battle against Google, and its uncertain attempt to take over Yahoo! all indicated Microsoft's inability to buy into a game it no longer controls. The Internet has become the biggest open-source system, a stupendous social network no less, but Mr Gates appeared too set in the old paradigm to play by its rules. So it has come time for him to leave, no longer at the top of his game, but nevertheless signalling the close of a remarkable chapter.