The British Transport Police (BTP) is investigating an alleged assault at St Pancras station in London.
The force said officers attended the scene on Monday night and found a man with “serious but non-life-threatening injuries”. It added that a 42-year-old male suspect had boarded a flight out of the country in the early hours of Tuesday morning.
It comes after footage emerged on social media appearing to show far-right activist Tommy Robinson walking back and forth near a motionless man lying on the floor at the station.
The clip does not show how the man ended up on the floor. Robinson, 42, whose real name is Stephen Yaxley-Lennon, has not publicly commented on the video.
BBC News has contacted Robinson for comment.
The BTP said its suspect was from Bedfordshire. It added that detectives were continuing to investigate the incident and bring the suspect into custody for questioning.
In the footage, a man who appears to be Robinson walks next to the person lying face-down on the floor, near some stairs. A commuter looks to be trying to stop the man thought to be Robinson from moving around and calls for help.
Two station staff members then approach the person on the floor, while Robinson walks away down some stairs and shouts: “He’s come at me, bruv.”
Robinson then starts coming back up the stairs, appearing to try to talk to the passing commuter who called for help. The video then ends.
Other videos posted on Robinson’s personal X account on Monday appear to show him in the same station, wearing the same blue shirt and bag that he looks to be wearing in the St Pancras video.
The BTP made no direct reference to the video in its statements.
Anyone with information about the incident has been urged to text 61016 quoting reference number 655 of 28 July.
A London Ambulance Service spokesperson said it received a call concerning reports of an assault at St Pancras at 20:40 on Monday.
They added: “We sent an ambulance crew to the scene and treated a man before taking him to a major trauma centre.”