Police have released an e-fit image of a man they want to speak to in connection with an indecent exposure on Clapham Common, close to the scene of a vigil in memory of Sarah Everard.
It happened at about 20:00 GMT on Saturday 13 March, near where hundreds of people had been attending the vigil.
Police describe the man as white, around 50 years old, approximately 5ft 6in (1.68m) tall, with grey hair.
Det Con Luke Flood urged people to check any photos or videos they took.
It is thought the man was wearing a bright red waistcoat or vest over a shirt and light coloured trousers.
"I would ask them to check any material they captured to see if they can identify the man described," Det Con Flood said.
"An incident of indecent exposure can be an extremely distressing offence for those who witness it and it is one police take very seriously.
"Officers have spoken to the victim in this case to offer her support and ensure she is kept updated with the progress of the investigation."
Initially, Met officers had not looked into the incident.
Georgina, who only wants to be known by her first name, told the BBC she had been ignored when she tried to report a man exposing himself as she was walking on Clapham Common Southside that night, close to the junction with Windmill Drive.
She said she went up to "about five or six police officers" to ask them if they could address the situation as she was feeling "very uncomfortable".
One male officer told her they had "enough with the rioters tonight".
The Met faced criticism for the way it handled the vigil after officers handcuffed and forcibly removed a number of women from the event.