The male station staff member at the ticket barrier of the station is said to have been sexually assaulted on December 16 at 4.40pm.
He prevented the worker from leaving the area and followed him until another employee intervened.
Police have today (January 13) released an image of a man who police would like to speak to and could have information that could help with their investigation.
Anyone who recognises him is asked to contact BTP by texting 61016, or by calling 0800 40 50 40 quoting reference 529 of 16 of December.
Information can also be given anonymously to Crimestoppers on 0800 555 111.
