British Transport Police officers investigating a violent assault on a member of staff at London Bridge Station have released CCTV pictures of the incident.
The railway employee, a 26-year-old man from East Ham, was attacked while on duty at the ticket barriers on the main concourse at London Bridge Station on Wednesday 30 July.
Detective Constable Rod Harbron, of BTP's workplace violence unit, said: "A man entered London Bridge Station at 3.20pm and approached the automatic barriers on the main concourse. He showed a 16-25 ticket but did not have the valid railcard to prove his age.
"When challenged by the ticket inspector, the man vaulted the barriers and punched him in the face. The attack was only stopped when members of the public intervened and the suspect made off – jumping back over the barriers and running from the station."
BTP officers arrived within minutes and searched the surrounding area but were unable to find the man.
Police say that they have been pursuing several lines of enquiry, including viewing CCTV footage from the cameras at the station and The Shard as well as speaking to witnesses.
DC Harbron added: "This was a violent and unprovoked attack which left the member of staff incredibly shaken up and with a nasty injury to his jaw.
"Members of rail staff do an incredibly important job and have the right to come to work every day without the fear of violence or abuse.
"BTP is committed to reducing assaults on staff. We work with train companies and Network Rail to improve safety at stations, and prosecute offenders."
"I want to hear from anyone who recognises the man in the video, as I urgently need to speak with him. I also would like to hear from any witnesses who have yet to come forward to police."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference S-SUB/B17 of 29/10/2014.
Information can also be passed anonymously to independent charity Crimestoppers on 0800 555 111.