Detectives have released an image of a man they would like to speak to in connection with a sexual offence on a bus in Lambeth.
The incident occurred on Saturday, 8 October at approximately 11:20hrs on a Route 159 bus as it drove through the vicinity of The High Parade, Streatham High Road, SW16.
The suspect boarded the Routemaster bus at Brixton Road, outside the KFC. He went to the upper deck and initially sat in front of two sisters aged 13 and 15 years old. After a short while he moved seats so he was across the aisle from them, near the middle of the bus.
He then put his hand down the front of his trousers and then exposed himself to the girls.
The girls were extremely traumatised by this and made their way to the front of the bus where they informed other passengers of what had happened. The suspect exited the bus using the rear staircase and the rear set of doors.
The suspect is described as a white man, aged in his early 20s, with short dark hair. He wore a dark puffa-style jacket over a dark jumper with a white 'D' on its front, blue jeans with a skull on them, and black and white trainers.
The incident is being investigated by detectives from the Met's Roads and Transport Policing Command.
Anyone with information is asked to contact Detective Constable Caroline Else on 07825 256 524, or Crimestoppers anonymously on 0800 555 111.
Alternatively you can tweet @MetCC with any information.
There have been no arrests.