Johnson's defeat of Ken Livingstone, who had been mayor for almost eight years, was a major blow to the Labor Party and Prime Minister Gordon Brown. The party lost heavily in Thursday's local elections.

The count in London took 15 hours because of the complicated system of first- and second-preference votes. Johnson, declared the winner just before midnight, took 42.48 percent of the first preference votes, while Livingston had 36.38 percent and Liberal Democrat Brian Paddick 9.63 percent, The Guardian reported.

An Old Etonian who moved from journalism to politics, Johnson became a celebrity on TV shows like "Question Time" and "Have I Got News for You." In Parliament, he was fired as shadow arts minister for lying about an affair and later became shadow education secretary.

His campaign combined Johnson's own charm and quick wit with the skills of conservative political strategists, The Telegraph said. They crafted a "doughnut" approach, wooing voters in outer neighborhoods who felt that Livingstone had ignored them.