Police have arrested a 42-year-old man on suspicion of assault after Roy Keane was allegedly headbutted during Arsenal’s victory over Manchester United at the Emirates Stadium on Sunday.

Keane was confronted in the stadium’s West Stand as he waited for a lift down to pitch level and his fellow Sky Sports pundit Micah Richards was seen restraining a man in a video posted on social media.

The pair continued their broadcasting duties after the incident, which happened just after United’s Alejandro Garnacho had an 88th-minute goal ruled out for offside.

A report in the Daily Mail said that the man allegedly aimed a headbutt at Keane and hit the former Ireland international on the chest and chin, but the 52-year-old brushed off any effect of the impact.

A Sky Sports spokeswoman 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.”

The Metropolitan Police confirmed that an investigation had been launched, saying in a statement: “Police are investigating following an assault that is alleged to have occurred at the Emirates Stadium during an Arsenal v Manchester United match on Sunday, September 3.” It later confirmed that an arrest has been made.

Keane had a tempestuous relationship with Arsenal during his playing days, often clashing with his rival captain Patrick Vieira.

Garnacho’s goal would have given United a 2-1 lead if it had not been ruled out, but Arsenal scored two goals in stoppage time to clinch a 3-1 win.

An Arsenal spokesman said: “We are aware of an incident that took place during our match against Manchester United on Sunday. The Metropolitan Police are conducting an investigation into the matter and we are fully co-operating with their enquiries.”