A man caught on video carrying out an "apparent racist attack" on the London Underground has been arrested after members of the public gave chase.
The clip was first posted on Twitter by Miqdaad Versi, assistant secretary general of the Muslim Council of Britain, who says someone else had sent it to him.
"Apparent racist attack on London Underground," he wrote. "Hope perpetrator is found and faces justice for this despicable unprovoked assault."
In the video, a bald man approaches a seated man and a woman while the train pulls up to Upton Park station. Without any warning he punches the man in the face, hard enough to knock his head back into the glass.
When the bald man exits the train and tries to escape the woman immediately gives chase, sprinting down the platform after him.
The video ends with the victim also chasing after his attacker.
It's not yet clear why someone was recording when the attack happened, but there is speculation there was some sort of altercation beforehand.
British Transport Police have since arrested a 33-year-old man.