Images on social media show Conservative mayoral candidate Susan Hall stretching out her hand to her Labour rival Sadiq Khan.
The pictures appeared to show victorious Mr Khan ignoring Ms Hall’s offer of a congratulatory handshake after the election results were read out.
A video of the event shows that Mr Khan did shake Ms Hall’s hand after he initially appeared not to see the Conservative candidate’s offer of congratulations.
The result of the May 2 London mayoral election was announced on Saturday May 4.
Images show Mr Khan, Ms Hall and the other mayoral candidates on stage, listening to the returning officer reading out the results of the ballot.
Photographs shared online show a moment where Ms Hall, who is stood to the right of the mayor, stretches out her hand towards Mr Khan, but he is looking to his left at that point and appears to miss the gesture.
A video of the moment clearly shows that Ms Hall then taps Mr Khan on the arm, at which point he turns his head, sees her hand and shakes it.
Mr Khan won the London mayoralty with 1,088,225 votes to Ms Hall’s 812,397. Third-place Rob Blackie, from the Liberal Democrats, received 145,184 votes, a little ahead of the Green Party candidate Zoe Garbett, who got 145,114 votes.
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