A man was punched in the head after apparently telling his attacker not to look at his computer screen.

The attack took place on a train between Clapham Junction and Gatwick (travelling through Croydon) on November 10.

Police said the 46-year-old man was attacked after he noticed another passenger was looking at his computer screen.

The victim asked him not to and a verbal altercation ensued.

As the victim went to move seat, police said the other passenger punched him in the head and then left the carriage.

The victim sustained bruising to his head and damage to his knee which he injured during the assault.

Now British Transport Police have released a picture of a man they believe could have information about the incident.

BTP ask that if you recognise him to call 0800 40 50 40 or text 61016, quoting reference number 570 10/11.