British Transport Police (BTP) said the man, who has not been named, was interviewed by investigating officers and cautioned over the offence following a public appeal for information which included CCTV images of a man and woman police wanted to talk to.

A spokesman for BTP said the force was yet to identify the woman involved in the offence, but was "following up a number of positive lines of enquiry".

The incident took place on September 28 shortly before 7.30pm.