A manhunt has been launched after a woman was sexually assaulted on the Tube and another was followed through an east London station.
Police say a 21-year-old woman was harassed by a stranger on two occasions in March.
Police have now linked the incident with a sexual assault at Marble Arch station on February 23.
On that occasion, a woman in her 40s, who suffers from arthritis, was approached by a Good Samaritan who offered to help her to the platform.
But, as they made their way through the station, he started to make sexual comments and touched her inappropriately. The attack happened at around 3.25pm.
British Transport Police have released CCTV of a man they want to trace over both incidents.
Investigating officer, Det Con Andrew Parkinson, said: “I would like to speak to the man shown in the CCTV images as he may have information which could help with the investigation into these two incidents, which we now believe are linked.
“The harassment against the woman at Walthamstow Central has left the victim feeling very intimidated and unsafe. Officers are supporting her as the investigation continues.
“It is vital that we trace the man responsible so that we can establish the full circumstances of the harassment incidents.
“Similarly we are still appealing for information regarding the sexual assault at Marble Arch.”
If you have any information, call police on 40 50 40 or text 61016 quoting reference number 175 21/04/17.