Sadiq Khan admitted that the Tory Party's chances of winning had "skyrocketed" just hours before polls closed.
The incumbent Mayor of London, who is battling for a historic third term, warned supporters that turnout for the elections appeared to be low.
He claimed this means that the chances of the Conservative candidate, Susan Hall, winning the election had increased significant.
Urging his supporters to go out and vote, he warned they could wake up to a "Tory nightmare".
Sadiq Khan admitted that the Tory Party's chances of winning had "skyrocketed" just hours before polls closed
PA
The London Mayor, who won the election by less than five per cent in 2020, warned that the election could be "extremely close".
A poll by Savanta published yesterday put him 10 points ahead of Hall.
The polloing said Khan would win 42 per cent of the vote, while the Conservative candidate was expected to win 32 per cent.
Londoners will have to wait until Saturday for the result of the election, which is expected to come in after midday.
Speaking to the Evening Standard earlier this week, Khan said he would happily take a narrow victory.
He said: "I’m quite clear, as someone who used to captain our cricket team: a win is a win."
Speaking after polls closed, Khan said: "Polls are now closed. Thank you to Londoners for voting.
"And thank you to every single Labour supporter and activist for your hard work today and across the campaign. Your energy has been inspiring."
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While Hall added: "Thank you to everyone who voted today and all who came out and helped, I’m forever grateful.
"No matter the result, I’ll never stop listening to you and fighting for a better London for all of us."
