By Sean Curran
Political correspondent, BBC News
Critics had questioned Mr Johnson's seriousness as a politician
Crikey! Boris Johnson is London Mayor.
The Conservative MP and journalist now has the biggest personal mandate of any politician in the country.
Dismissed by political opponents and many in the media as little more than a music hall turn, he confounded his critics by running a gaffe-free election campaign.
This victory gives the Conservative Party a clean sweep: the largest share of the vote; the most councillors; and control of the capital.
At first glance the mayoral contest is of little relevance to people living and working outside London but the political parties and the media have invested it with a national significance.
Does Boris Johnson's success mean the country is ready to embrace David Cameron's Conservative Party?
It also vindicates Mr Cameron's decision to back a maverick candidate.
The test now is for Boris Johnson to deliver his policies on the bread and butter issues of transport and crime.
During the campaign the tousle-haired Old Etonian was restrained and professional.
Mr Johnson is now the national and international face of London, one of the world's greatest cities. He will now face media and political scrutiny
There was little evidence of the flamboyant Wodehousian personality that has won him lucrative work as a newspaper columnist and a berth on television quiz shows.
Has the old Boris gone forever? What happens if he returns? And what will it mean for David Cameron and the Conservatives?
The Tory leader does not want to spend the two years in the run-up to the next general election having to defend, or distance himself from, the London Mayor.
Mr Johnson is now the national and international face of London, one of the world's greatest cities. He will now face media and political scrutiny.
As Londoners prepared to vote The Guardian newspaper published a series of articles urging people to reject Mr Johnson.
Similar articles appeared in other papers. The warning was clear: you may think you are voting for a charming Bertie Wooster-like figure but in fact you are about to hand power to a less pleasant character.
This is moment to trot out what is perhaps the most famous journalistic cliché of all - only time will tell.
For now, though, Mr Johnson's win is a boost for the Conservatives that brings them one step closer to power.