A short video has emerged on Twitter that appears to show a Millwall supporter punching a Tottenham fan following the FA Cup match between the two sides, which Spurs won 6-0.
The seven-second video appears to have been recorded after the match, with a man wearing a flat-cap assaulting two Tottenham supporters singing an anti-Millwall song.
The thug approaches the two men singing before punching one of them in the face, with enough force to knock the man to the ground.
The man who throws the punch then quickly re-joins the throng of Millwall supporters leaving the ground.
The Twitter user who posted the video to the social media platform claims that the man who punched the Tottenham fan was a Millwall supporter.
The video has already been viewed thousands of times and the Metropolitan Police has confirmed that they are aware of the footage, with several members of the public reporting the video to them.
Violence had already flared between the two sets of supporters ahead of kick-off, with fans clashing ahead of kick-off.
Police in riot gear had to separate fans outside the stadium, as flares and coins were thrown.
Hundreds of police officers meanwhile patrolled the streets around the stadium, while inside White Hart Lane all stewards were instructed to wear plastic hard hats.
Racist chanting directed from the travelling support to Spurs forward Son Heung-min had earlier overshadowed the match, with Millwall manager Neil Harris quick to condemn the abuse.
Son scored a hat-trick at White Hart Lane as Spurs thrashed the Lions 6-0, but their victory was marred by abusive songs aimed at the South Korean from the visiting supporters.
Millwall fans were heard chanting "DVD" and "You're selling three for a fiver" at Son during the first half, thought to be in reference to the racist stereotype of traders selling bootleg copies of films.
Son delivered the perfect response with his treble while further goals from Christian Eriksen, Dele Alli and Vincent Janssen secured an emphatic success for Mauricio Pochettino's team.
Harris admitted after the match he had not been aware of the chants but said they would be a blot on Millwall's excellent run in the competition.
"I didn't hear anything, but the club, we won't condone that," Harris said.
"We came here in the right spirit, to enjoy an FA Cup quarter-final, so if that's proven to have been to the detriment to the competition then I'm sure it will be left to the authorities. We just want people to enjoy the game.
"Of course it's a shame, for both of us - Mauricio wants to be talking about his team's quality.
"The focus comes away from what we've achieved in the competition. It's wrong in society and it's wrong in football."
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