Police are hunting two men who punched a passenger who asked them not to vape on a London Overground train.
Just before midnight on July 10, a group of young men were vaping on the northbound service when they were challenged by a member of the public.
Two of the men then punched the passenger, before a second group of young men boarded the train and a fight broke out between the groups.
The service was at Harrow and Wealdstone station at the time of the incident.
On Thursday, officers investigating the assault released images showing two men they are keen to trace.
A British Transport Police (BTP) spokesperson said: “Officers believe the man in the CCTV images may have information which could help their investigation.”
They urge anyone who recognise the men or who have information about the incident to contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 637 of 10 July.
Alternatively, call Crimestoppers anonymously on 0800 555 111.