A sex attacker assaulted a fellow tube passenger who asked him whether he was on the correct train.

British Transport Police said the male victim had boarded a northbound Northern Line tube at Kennington at around 10.25pm on August 6. 

While on board, he approached a man who had also boarded at Kennington to ask whether he was on the correct train.

The man then sexually assaulted him.

The victim moved to another carriage and the man left the train at Golders Green station.

Police have issued an image of a man who may have information that could help their investigation. 

If you recognise him, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 2300092243.

Information can also be given anonymously to Crimestoppers on 0800 555 111.