A man repeatedly groped a woman on a train for 10 minutes as they travelled through London.
Police said the woman was attacked on a train between Clapham Junction and Richmond as they appealed for information to catch her attacker and to trace a man who came to the victim's aid.
The woman was sexually assaulted several times near the rear of the train between 5.28pm and 5.38pm on November 3. Police believe the attacker stayed on the train after she disembarked, and got off later at Twickenham.
The man was Asian, around 5ft 10ins tall and of average build. He is believed to have been aged in his 50s and wore a grey flat cap and grey jacket.
The victim was comforted by another passenger after the attack and police also want to trace him.
