Detectives are hunting for a man suspected of carrying out a series of sexual assaults on teenagers on board buses in north London.
Scotland Yard said the same suspect was believed to have been responsible for at least five offences on crowded services between January and March.
In the first alleged incident on January 25, an 18-year-old woman was assaulted while standing up and later sitting down on a route 279 bus. The suspect had boarded at about 6.30pm at Tesco Ponders End and got off at Angel, Edmonton.
Two 14-year-old girls were also attacked on the same route in separate incidents on the mornings of January 29 and February 21.
On the first occasion, the suspect had boarded at about 7.20am, and the schoolgirl was assaulted while on the bus between Scotland Green and Enfield Highway - while in the second incident, the teenager was targeted while standing up, having boarded at Nightingale Road at about 7.45am.
On March 12, a 15-year-old girl was the victim of an assault on a route 34 bus between Cambridge Roundabout and Green Lanes after 8am.
In a fifth alleged incident, at just before 9am on March 15, the suspect was on a route 102 bus and was said to have been touching himself while watching a 17-year-old girl.
The Metropolitan Police said the suspect had short black hair and a thin beard along his jaw, and was wearing a two-tone padded blue jacket and blue jeans.
An image has been released of a man they would like to trace in connection with the investigation.
Detective Sergeant Edward Coleman said: "We know of at least five offences committed by the same suspect on crowded buses.
"We would like to hear from anyone who may know this man's identity.
"We also want to hear from anyone who may have been the victim of a sexual assault while travelling on a bus."
Anyone with information should contact police on 101 quoting reference CAD 2343/12Mar or call Crimestoppers anonymously on 0800 555 111.