Amina du Jean has never shared her real identity online. Yet somehow, the Metropolitan Police who recently turned up on her doorstep knew her full name and university. They hadn’t come to arrest du Jean – as an independent sex worker, they’d have no grounds to – but rather to perform a “welfare check”. “They said they were concerned that I was a victim of trafficking”, she tells me.

What they were really saying was that they were watching her.

Du Jean can’t be sure of how the police identified her, but she can guess. As a sex worker and former J-Pop idol, her face is all over the internet.

A decade ago, being “face out” might have been a bold statement for sex workers. Recently, it’s become a serious liability. As Gracie Bradley, policy and campaigns manager for human rights organisation Liberty put it at a recent event, police use of facial recognition technology is “turning us all into walking ID cards”.

The algorithmic dot-joining that advertises you baby clothes before you even know you’re pregnant might be creepy to most people, but can have life-threatening consequences for sex workers. In 2017, for example, Facebook began suggesting a Californian sex worker’s clients to her as “People You May Know”. What if they’d suggested her to them, too?

At the same time, the migration of sex work to online platforms has made it possible for states to survey workers on an industrial scale – often, as in du Jean’s case, under the guise of sex trafficking crackdowns. Days after the US’s Department of Homeland Security seized the adult listings site Eros in 2017, dozens of sex workers with profiles on the site were detained and deported at the US border.