A man reportedly "exposed himself" in front of a 14-year-old girl and her mother on a train between Gatwick Airport and Hitchin.
British Transport Police has launched an investigation into the incident, which is thought to have taken place at around 7pm on Saturday, August 27.
A police spokesperson: "A man sat near a 14-year-old girl and her mother on board the train.
"During the journey the man exposed himself inappropriately to the 14-year-old girl while staring at her.
"The victim’s mother confronted the man, who then got up and walked away."
Police have released a picture of a person they would like to speak to in connection with the incident. He was on board the Hitchin-bound train and may be able to help with their investigation.
The BTP spokesperson added that anybody with information can contact the force by texting 61016 or calling 0800 40 50 40 quoting reference 548 of August 27.
Reports can also be made 100 per cent anonymously via CrimeStoppers on 0800 555 111.
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