A BTP spokesperson said: “At 10.10pm on Tuesday 6 July, an intoxicated man boarded the train at Wembley station. During the journey, he approached a woman travelling alone on the carriage and sexually assaulted her. He then got off the train at #Solihull Station.
“Officers believe the man in the CCTV images may have information which could help their investigation.
“If you recognise him, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 2100049135 of 06/07/21.
“Alternatively, you can call Crimestoppers anonymously on 0800 555 111.”