FOOTAGE shows Roy Keane's incredible reaction to allegedly being headbutted by a fan - with the pundit shrugging off the "attack" and joking on camera just minutes later.
The Sky Sports pundit was seen chatting and laughing with Arsenal star Declan Rice as they went live for a post-match interview.
Consummate professional Keane looked relaxed as Rice talked about Arsenal's 3-1 win over Manchester United - and even joked that Rice's strike should have been ruled an own goal
But he was left "shaken" after he was allegedly headbutted by a fan, sources said.
Roy Keane’s attacker exclusively unmasked by The Sun
Micah Richards was seen pinning a man against a wall during a confrontation inside the Emirates Stadium yesterday.
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Both pundits were left shaken following the incident, Sun Sport understands.
Sky is also understood to be beefing up its security moving forward.
The fan, meanwhile, fled the scene in a crowd with police and Arsenal now combing through CCTV footage to find him.
Keane and Richards had been waiting near a lift at the members-only Highbury Bar, at the top of the West Stand, when the incident took place.
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They were making their way towards pitchside to give their post-match thoughts as part of Sky's coverage as the Premier League clash reached its final stages.
But the pundits began returning to the Sky studio to watch replays of Alejandro Garnacho's late goal for United, only for his strike to be later ruled out for offside.
Richards is said to have been "acting to defuse a situation", a Sky Sports spokesperson said.
The fan was prevented from inflicting any serious damage on the United legend.
Arsenal are cooperating with authorities with the investigation underway.
A club spokesperson added: "We are aware of an incident that took place during our match against Manchester United on Sunday.
"The Metropolitan Police is conducting an investigation into the matter and we are fully cooperating with their enquiries."
A spokesperson for Sky Sports said: "We understand the police are investigating an alleged assault by a member of the public immediately preceding the footage circulating on social media.
"In the footage seen, Micah Richards was acting to defuse a situation."
Keane and Richards played for fierce rivals on the pitch, but have former an unlikely bond since the ex-City defender joined the Sky Sports punditry team.
They regularly work on Sky's Super Sunday programme and will likely be back on TV screens together after the international break on September 17.
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Arsenal ended up running out 3-1 winners thanks to injury time strikes from new-signing Declan Rice and substitute Gabriel Jesus.
Marcus Rashford had earlier given United the lead, before Martin Odegaard cancelled out his strike less than a minute later.