A woman has been filmed chasing a man along a London underground platform after witnessing an attack.

Footage has emerged of a man punching a man in the face whilst sat on the tube unprovoked.

The incident occurred on 17 October just before reaching Upton Park station.

A woman seated next to the victim then chases the perpetrator down the platform.

The incident was caught on video and was subsequently posted on social media.

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British Transport Police said in a statement, “We are investigating an assault after a video was brought to our attention.

“The incident happened on a tube at Upton Park tube station at around 3.40pm on 17 October 2016.

“A 33-year-old man has been arrested on suspicion of assault occasioning ABH and using threatening / abusive words / behaviour or disorderly behaviour likely to cause harassment, alarm or distress. He has been bailed until 14 November.

“If anyone has any information about the incident, please call contact us via 0800405040 quoting ref 554 18/10/16.”