Police are investigating after a man exposed himself to a schoolgirl on a train between Baker Street and Wembley Park.

British Transport Police has released CCTV images of a man they believe holds key information about the incident where a man exposed himself to a 13-year-old girl and followed her when she changed trains.

The teenager was dressed in her school uniform and was travelling between King's Cross and Wembley Park on the Metropolitan Line at around 10.40am on July 4.

Police want to speak with this man who may have key information that could help their investigation

A man had boarded the train at Baker Street and sat opposite the young girl, staring at her before standing up and exposing himself to her.

The girl left the train at Wembley Park frightened, and crossed over to the Jubilee Line platform heading northbound, but the man followed her, walking on to the same carriage.

At the last moment, the girl switched carriages, only to have the man stare at her through the window between carriages.

The girl ran out at Kingsbury station where the man also alighted.

A schoolgirl was travelling on a Metropolitan Line train at 10.40am when a man exposed himself to her

Investigating officer Detective Constable Marc Farmer said: “This poor schoolgirl was left frightened by the man’s behaviour.

“No one should be subjected to this. I am pleased that the girl had the courage and confidence to report the incident, for us, every report builds a picture.”

Anyone with any information should contact British Transport Police on 0800 40 50 40 or text 61016 citing reference 159 of 02/08/17.

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