Sadiq Khan is widely expected to give Labour a glimmer of hope after a crushing blow as the Tories romped to victory in the Hartlepool by-election.
Labour's Mr Khan is running for re-election, with polls in the final days of the campaign suggesting he has a firm lead over Shaun Bailey, his Conservative opponent.
By 9.30pm on Friday, seven the 14 constituencies had declared, with Sadiq Khan having received 487,104 first preference votes (39 per cent) to Shaun Bailey's 462,837 (37 per cent).
It has raised hopes among Tory supporters that the result could be closer than expected.
Check back to this page throughout Friday and the weekend to see how the count is progressing.
Mr Khan faces opposition from the Conservative's Mr Bailey, who is a former adviser to David Cameron and other candidates include the actor Lawrence Fox and Count Binface.
With the Labour Party at war over the direction of the party, Mr Khan's re-election would be at least some consolation to under-pressure leader Sir Keir Starmer.
On Thursday, Mr Khan tweeted: "London: reports show that voter turnout is low across our city. If you love London & what we stand for, please come out and vote for it.
"We had a Tory mayor just five years ago - if you don't vote, they could win again. Already voted? Please RT and ask friends to vote Labour."
He later said: "To the thousands of Labour activists & supporters who joined us on the most unique election campaign of my lifetime.
"To the Londoners who came out to lend me your vote for the better and brighter future our city deserves. Thank you. I truly am grateful."
The London Mayoral elections, in pictures
The London Mayor candidates
Shaun Bailey (C)
Sadiq Khan (Lab)
Luisa Porritt (LD)
Sian Berry (Green)
Kam Balayev (Renew)
Vanessa Hudson (AWP)
Count Binface (Binface)
Richard Hewison (EU)
David Kurten (Heritage)
Piers Corbyn (LLL)
Brian Rose (LRP)
Valerie Brown (Pink)
Laurence Fox (Reclaim)
Steve Kelleher (Soc Dem)
Mandu Reid (Women)
Niko Omilana (Ind)
Max Fosh (Ind)
Nims Obunge (Ind)
Farah London (Ind)
Peter Gammons (UKIP)
The 2016 London Mayor vote, in numbers
Turnout: 2,596,961 (45.31%)
First Count: Khan (Lab) 1,148,716; Goldsmith (C) 909,755; Berry (Green) 150,673; Pidgeon (LD) 120,005; Whittle (UKIP) 94,373; Walker (Women) 53,055; Galloway (Respect) 37,007; Golding (Brit) 31,372; Harris (Cannabis) 20,537; Furness (BNP) 13,325; Zylinski (Ind) 13,202; Love (Love) 4,941.
What time are the London mayoral election results announced?
Vote counting started on Friday, May 7, at 7am.
Due to coronavirus precautions that are being implemented at polling stations, a final result in the mayoral is not anticipated until the afternoon of Saturday, May 8, at the earliest, but a Sunday result is also possible.
Results from seven 'First Past The Post' seats (FPTP) in the London Assembly may be declared on Friday evening - these are Bexley & Bromley, Brent & Harrow, Ealing & Hillingdon, Havering & Redbridge, Lambeth & Southwark, North East and West Central.
The remaining seven FPTP seats will be declared on Saturday afternoon and evening. These are Barnet & Camden, City & East, Croydon & Sutton, Enfield & Haringey, Greenwich & Lewisham, Merton & Wandsworth, and South West.
The London-wide Proportional Representation top-up seat result may come late on Saturday, but could be on Sunday.
About our results
Our results data are provided by the Press Association. Changes are calculated against a council's or parliament's composition at the time of the election, rather than against the composition resulting from the previous election. The Press Association only collates results for elections already scheduled to take place for May 6, 2021, so some council by-elections may not feature in our data.