Labour's Sadiq Khan has broken the Conservatives' eight-year hold on the London mayoralty by defeating Tory rival Zac Goldsmith.
The Tooting MP will become the first Muslim mayor of London after he emerged as the victor over Mr Goldsmith and 11 other contenders.
Speaking on Sky News, election analyst Michael Thrasher said: "We're looking at the distribution of first votes and Khan is a long way ahead of Goldsmith on that.
"It is mathematically impossible for Goldsmith to overtake Khan."
The result follows an at times bitter mayoral bid from both camps, with Mr Goldsmith's campaign being labelled "vile" by Labour leader Jeremy Corbyn.
Mr Goldsmith and David Cameron in turn sought to link Mr Khan with Muslim "extremists" during the lead up to Thursday's poll. Mr Khan was the bookmakers' favourite to win the mayoral race. He is the son of a Pakistani bus driver who grew up on a council estate.
He has been the MP for Tooting since 2005, and has held the post of transport minister, shadow justice secretary and shadow minister for London.
His campaign focused largely on transport and providing affordable housing for Londoners.
In the lead up to the poll, he vowed to build more homes, provide starter houses for under £450,000, and ring-fence new homes on brownfield sites for Londoners.
He also pledged a four-year fare freeze on transport and better relations with unions to end strikes.
Earlier, outgoing mayor Boris Johnson thanked the capital for his eight years in office as he sent his final messages from the official London Mayor Twitter account.
2/2 It’s time to sign off from City Hall – it’s been the most amazing privilege to be your Mayor. You can follow me on @BorisJohnson
— Boris Johnson (@MayorofLondon) 6 May 2016
"It's time to sign off from City Hall - it's been the most amazing privilege to be your mayor," he tweeted.
