British Transport Police are now investigating following the assault on Tuesday, November 26 at 1.45pm.
A man is reported to have inappropriately touched a teenage girl on the knee and thigh. He then took photos of her face and legs before touching her hands and her legs a second time.
Officers have released CCTV images of a man they would like to speak to.
Police would like to speak to the man in the image who may have information that could help their investigation.
Anyone who knows him is asked to contact BTP by texting 61016 or by calling 0800 40 50 40 and quoting reference 1900101889.
Alternatively, call Crimestoppers anonymously on 0800 555 111.