A 54-year-old woman was slapped across the face on a busy Northern line Tube after asking a man to turn down the volume on a video he was watching on his phone.

Police believe the southbound train travelling on the High Barnet branch between Camden Town and London Bridge would have been very busy when the incident occurred at around 7.10pm on Monday, April 28.

The suspect is black, about 40-years-old, of stocky build with a shaved head.

He was wearing a black suit, red stripy shirt and glasses and was carrying a brown briefcase.

PC Matthew Kaye, of British Transport Police, said: “The victim boarded the train at Camden Town at around 7pm and sat close to a man who was watching a video on his mobile phone.

“A short time later an altercation occurred when the victim asked the man to turn the volume down and he slapped her across the face.”

PC Kaye added: “This was a very unsettling experience for the victim and we are working hard to catch the man responsible.

“There were a number of other passengers in the carriage at the time and I would urge them to come forward as they might have crucial evidence which could assist our investigation.”

Anyone with information can call police on 0800 40 50 40, or text 61016, quoting reference TSUB/B7 of 04/06/2014, or call Crimestoppers anonymously on 0800 555 111.