Police are hunting a man who repeatedly punched a member of staff in the face at Aylesbury railway station.
Officers were called to the station shortly before 9pm on Friday following a report of an assault.
By the time they arrived, the suspect had fled the scene.
The male victim suffered minor cuts and bruises.
British Transport Police are studying CCTV of the incident as part of their investigation.
The suspect is described as white, aged between 20 and 25 and around 6ft tall. He spoke with an Irish accent.
Anyone with information should call BTP on 0800 40 50 40 quoting 615 of 20/09/2013.