Images have been released of a man British Transport Police officers are hunting following an attack at Farnborough Main railway station which left the victim with a partially-severed ear.
Investigators hope CCTV pictures showing a large man wearing a bright orange shirt will help solve the unprovoked attack that took place on board the 6.42pm Waterloo to Basingstoke service on Saturday July 5.
Detective Constable Phil Bibbings, leading the investigation, said: "A 62-year-old man from Farnborough was travelling home from London with three friends.
"As the train pulled into Farnborough, they were approached by a man holding an empty beer glass who began verbally abusing them.
"During the altercation the man struck the victim across the face with the beer glass, causing it to smash.
"He then continued to hit the man with the remaining broken glass, possibly cutting himself in the process."
Fellow travellers then intervened to help the victim and the attacker fled the train at Farnborough and entered a taxi with two other men.
"The victim's ear was almost cut clean off during the attack and he required multiple stitches at hospital," said the detective.
"The unprovoked nature of the assault is of great concern and we are working hard to catch the person responsible and bring them to justice."
Police believe the suspect has a 'broad Scottish accent', and may live or have connections in the Woking or Camberley areas.
DC Bibbings added: "Who is the man in the orange t-shit?
"I believe he could have crucial information about what happened on that train, which will greatly assist our investigation. If you recognise him, please get in touch.
"I am keen to speak to anyone who witnessed the incident and has not yet come forward to police."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference SSUB/B11 of 27/08/2014.
Information can also be passed anonymously to the independent charity Crimestoppers on 0800 555 111.