The incident occurred at 10.35pm on Saturday, March the 2nd.
A man accompanied by a woman started talking to another man at the exit of platform two,
He then demanded the victim hand over his phone and produced a knife and the victim handed his device over.
Police believe that the two men and the woman in the CCTV picture above may have information to assist their investigation and are asking them, or anyone who recognises them, to get in touch.
Anyone who recognises them is asked to contact BTP by texting 61016, or by calling 0800 40 50 40 quoting reference 768 of 2 March.
Information can also be given anonymously to Crimestoppers on 0800 555 111.
