At around 8pm on 7 July, the victim – a man who suffers with learning disabilities – was sat in a carriage when another man sat opposite him.
That man took off his shoe and proceeded to touch the victim inappropriately with his foot.
It left the victim very distressed.
Officers would like to speak to the man in this image as they believe he may have information which could help the investigation.
Anyone with information is asked to contact BTP by calling 0800 40 50 40 or texting 61016 with reference 261 of 7 July.
Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.