A Leyland man at a railway station was repeatedly hit on his head with a metal bar.
The 44 year old ended up in hospital after a serious assault while he waited for a train last month.
Detective Constable Mick Millward, investigating officer for British Transport Police, said: “At around 7pm on Friday, October 26, the victim was waiting for a train at Chorley station when he noticed a group of three men standing close to him.
“Unprovoked, one of the men suddenly punched him in the face, resulting in a struggle between the men and the victim falling to the floor.
“A second man then produced a metal bar from on him and started to hit the victim around the head with it several times, causing heavy bleeding.”
The man was taken to Chorley and South Ribble District General Hospital in an ambulance, and was discharged the following day.
Two men have been arrested and released on police bail pending further enquiries into the incident.
British Transport Police have released a description of a third man they would like to speak to as part of their enquiries.
DC Millward said: “There was a third man present who was trying to pull one of the men away from the victim during the attack.
“We believe this man will have key information about the incident and we are keen to speak to him.
“He is described white, aged around 20-years-old and approximately 5ft 6in tall.
“At the time he was wearing a dark top with a grey hood, dark trousers, and wearing JD string sports bag across his body.
“This was a vicious, unprovoked attack on the victim, which left him hospitalised.
“I’d urge anyone with information about the attack, or who saw anything at the time, to please get in touch.”
Police have conducted several lines of enquiry into the attack and have since arrested a 26-year-old man and a 23-year-old man, both from Preston, in connection with the incident.
Anyone with information should call Crimestoppers on 0800 555 111.