After being chased off a Tube train following a torrent of sexist and homophobic abuse, Zan Moon decided to take action.
Although she reported her abuser to British Transport Police (BTP), her case was thwarted after the CCTV footage was automatically deleted within 72 hours.
She then decided to set up a forum for women to anonymously report similar incidents and was inundated with 200 responses in just two weeks.
She has now called on the police and City Hall to take more action.
Ms Moon was travelling with her partner on the Underground in January when she was targeted by a man in his 40s and ended up having to leave the carriage to get away.
"It made me feel extremely unsafe," she said. "I felt violated.
"I called out for help multiple times and the carriage was full of men but nobody did anything to help so I had to leave the Tube, just for my safety and my partner's safety.
"I was left just feeling horrified and uncomfortable in my own skin."
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The Night Tube began running in 2016
Despite reporting the crime the next day and giving a statement, including a description of the man, Ms Moon said she "never really heard back" about what happened to her case.
Nevertheless, she said the experience "lit a fire in my belly" and inspired her to set up Screengrab Them, where women can anonymously report harassment.
Within a fortnight, she said hundreds of responses had come in, which included bystanders intervening in just 1% of cases.
"Out of 200 responses, only two people had anyone intervene," she said, adding that "81% had people around them who saw it happening, but chose not to do anything."
Ms Moon collated the data and sent it to the London mayor asking for change.
Having met Deputy Mayor for Transport Seb Dance, as well as the Met and British Transport Police, Ms Moon said she generally felt positive that the authorities were "taking it seriously".
"There are just a few sticking points where we're not seeing eye to eye, such as the CCTV, which I feel really strongly about," she said.
"We're in 2022 and we can send a person to the moon and back, yet you're telling me we can't upgrade CCTV so it lasts longer than three days.
"That's such a small window for victims to come forward and feel confident to talk about it, let alone report it."
She added that there was also "zero CCTV" on the Central line where "sexual harassment is most prevalent", and called for police to start patrolling carriages rather than stations.
A spokesperson for Sadiq Khan said the mayor believed "violence and harassment towards women" was a "deep cultural problem in our society", and preventative work was "an absolute priority".
They said: "The mayor is working with TfL and the police to stamp out this predatory behaviour and ensure a zero-tolerance approach to all forms of sexual harassment across the whole network."
Siwan Hayward, TfL's policing director, said there was a zero tolerance approach and the transport body supported Mr Khan's calls to make sexual harassment in public spaces a criminal offence.
She said: "As well as proactive police patrols taking place across public transport, we work with the police to pursue all sexual harassment offences using our extensive network of CCTV and will be continuing to deliver sexual harassment training to all frontline staff."
BTP Det Insp Sam Painter said police were "working tirelessly to stamp out this unacceptable behaviour".
He added: "We have enhanced patrols of uniformed and specially trained plain clothes officers across the network day and night to catch offenders and reassure passengers as they travel.
"It's vital that passengers continue to report these incidents to us for us to be able to take action - we can identify hotspot locations, target our patrols, and bring more offenders to justice."
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