An Arsenal official confirmed afterwards that once the judicial process is over, the fan will be banned for life from the Emirates Stadium.
“We utterly condemn the behaviour of the individual who ran onto the pitch and approached Chris Smalling during today’s match," said a club statement. "We would like to apologise to Chris and Manchester United, and are pleased that he was apprehended and arrested.
"We will be working closely with the Metropolitan Police in their investigation. The individual will also be banned from Arsenal matches home and away. Our matchday staff receive ongoing training on managing incidents such as this."
Player ratings from Arsenal vs Manchester United
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Arsenal manager Unai Emery also condemned the supporter in his post-match press conference. “I don’t want that,” he said. “It is not in my control. I am proud of every supporter who helped us.”
The Metropolitan Police confirmed the arrest in a statement. It read: "A man has been arrested on suspicion of common assault and pitch invasion following an incident during the Arsenal v Man Utd game at the Emirates Stadium today. He is currently in custody at a north London police station."
The incident at The Emirates was the second on an unpleasant day for English football. Jack Grealish was punched by a supporter in Aston Villa's 1-0 win against Birmingham at St Andrew's during a highly-charged derby.
The man was arrested and Aston Villa called for strong action to be taken.
Jack Grealish punched by fan during Birmingham City vs Aston Villa
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"Aston Villa Football Club is appalled by the disgraceful attack on Jack Grealish during today’s game," said the Midlands club in a statement.
"A red line has been crossed by this cowardly on-field assault on a player, which is unprecedented in English football.
"We trust the perpetrator will feel the full force of the law and the authorities investigate the circumstances surrounding today’s deplorable incident.
"Local rivalries are part of the fabric of the game however, as we are sure our friends at Birmingham City would agree, to have a player’s personal safety placed under such jeopardy is a serious cause for concern for the entire football community."
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