Police have arrested a 42-year-old man after Roy Keane was reportedly headbutted on Sunday.
The Manchester United legend was working for Sky Sports during their 3-1 Premier League defeat to Arsenal.
Footage then went viral on social media of Micah Richards holding a man by his collar, with Keane also in the footage.
It has since been widely claimed that Keane was headbutted by a man in the Highbury Bar at the Emirates Stadium, which is for members only.
Roy Keane was working with Micah Richards for Sky Sports when the incident took place
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The Metropolitan Police released a statement that read: "Police are investigating an incident at Emirates Stadium on Sunday, 3 September, during which a man was assaulted.
"On Monday, 4 September, a 42-year-old man was arrested on suspicion of assault (ABH).
"The man has been taken into police custody. Enquiries are ongoing."
An eyewitness told the Daily Express that a small amount of blood was seen on the floor after the incident.
"The incident occurred shortly before the 90th-minute mark in the Highbury Bar for platinum members.
"The fan seemingly tried to head-butt Roy Keane.
"I then saw a mark between his eyebrows. Micah Richards stepped in and pushed the fan back against the door.
"I heard the altercation and I was shocked to see the individuals involved.
"Richards was very forceful at keeping the fan from attacking Keane and neither their security nor the door security could split the two apart. Keane was asking nearby staff to call the police.
"Additional security was called in and Richards and Keane followed until the fan was escorted downstairs via the escalator out of the building.
"Presumably, Keane and Richards then returned to their Sky Sports duties via the exit that they came in through next to where the video is shown.
"Afterwards, we noticed a small amount of blood on the floor on the route where the fan was led out.
"Seems like Micah Richards was acting as Roy Keane's bodyguard."
Sky insist Richards was working to diffuse the situation.
“We understand the police are investigating an alleged assault by a member of the public immediately preceding the footage circulating on social media," said a spokesperson.
"In the footage seen, Micah Richards was acting to diffuse a situation.”
During his playing career, Keane had a tense relationship with Arsenal with United and the Gunners among the best teams in the country at the time.
The former Republic of Ireland midfielder would often clash with Arsenal hero Patrick Vieira during the height of United's rivalry with the north London side.
And Keane was also involved in one of the Premier League's most-memorable pre-match moments against Arsenal, too.
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Roy Keane resumed his punditry duties after the alleged incident in Arsenal's win over Man Utd
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Keane clashed with Viera in 2005 and had to be restrained when he accused the Frenchman of trying to bully Gary Neville.
United would then run out 4-2 winners during the match at Highbury with a young Cristiano Ronaldo scoring twice.
