Police are seeking a pervert who pretends to be asleep on the Tube then exposes himself to women.
The indecent exposures have happened on four occasions on the Metropolitan and Jubilee lines between June 27 last year and March 10.
In each, the man has sat opposite a lone woman, pretended to go to sleep and then has exposed himself, British Transport Police said.
He has touched himself inappropriately, whilst watching the women through half-closed eyes.
The offences took place on trains between Baker Street and Northwood Hill, West Harrow to Finchley Road and Green Park to Wembley Park.
Officers have released a CCTV image of a man they wish to speak to who they believe may have information which could help the investigation.
Anyone with information is asked to contact BTP by calling 0800 40 50 40 or texting 61016 with reference 328 of 24 April.
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