According to the British Transport Police, a man had slapped another passenger as the train approached the platform on August 24 between 11.40pm and 11.50pm.
The men then started fighting on the platform and another member of the public tried to intervene and break up the fight.
However, this person was assaulted in the process.
The man then left the station and boarded a bus.
Police have released an image of someone who may have information that could help their investigation.
Anyone with information or who recognises the man is asked to contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference number 838 of 24 August.
Alternatively, contact Crimestoppers anonymously on 0800 555 111.
