These are the images of a man police want to question in relation to a sexual assault last month.

The alleged attack happened at Cricklewood mainline station just after 6am on August 31, and British Transport Police have released the CCTV pictures to help their appeal for information.

Police said a 23-year-old woman was waiting in the ticket office for a train into central London when she was approached by a man riding a red mountain bike.

The man began having a conversation with the woman before getting off his bike and pulling her into the station subway where she was sexually assaulted.

A BTP spokesman said the man was disturbed by rail passengers getting off an arriving train and made off on his bike.

He is described as in his early twenties, black, 5ft 8ins tall, with a slim build, short black hair and unshaven. He was wearing dark jeans and a white, short-sleeved t-shirt with a motif on the front.

Detective Sergeant Mark Barton, investigating officer from BTP, said: “The woman was not physically injured, but she was understandably very frightened and shaken up by what happened.

“We believe the man pictured in these images could assist us with our enquiries and I would appeal to anyone who may have information, however insignificant they may think it is, to come forward and contact police.”

Anyone with information is asked to call BTP on 0800 40 50 40 quoting incident number 92 of August 31. Information can also be passed to Crimestoppers anonymously on 0800 555 111.