A 15-year-old girl was sexually assaulted as she travelled to school on the Tube, police said.
The teenager was groped on a rush hour Victoria Line train by a man who followed her from Stockwell to Oxford Circus.
Police said the man followed and then "stood over" the girl as she changed lines, until she eventually left Oxford Circus on a Bakerloo Line train.
Detectives today released a CCTV image of a man they want to speak to in connection with the incident, at around 8am on Tuesday, June 9.
DC Andy Parkinson said: "Fortunately incidents like this are rare, but this was a frightening experience for the girl and one which she should not have had to put up with.
“I would like to commend her for contacting police and would now ask the public to help us."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference TSUB/B10 of 29/06/2015. Information can also be passed anonymously to the independent charity Crimestoppers on 0800 555 111.
