London’s special status is nothing new. In the 1500s Henrys VII and VIII shut down Southwark’s brothels, or “stew houses”, to try to stop the spread of syphilitic sores. A study in 2020 estimated that in the 1770s a staggering one in five Londoners was likely to have had “the pox” by the age of 35, against 8% of people in the provincial city of Chester and less than 1% in rural areas. Given that gonorrhoea is around four times as infectious, a majority of Londoners may have had an STI, marvels Simon Szreter of the University of Cambridge, the paper’s lead author.

Thanks to antibiotics, among other things, STI rates today are a fraction of what the Georgians endured. But London is still a relative hotbed. As in the 18th century it has a young, fast-growing population with large social networks to spread STIs. Rates are no longer highest among squaddies and scullery maids but in other marginalised groups (eg, in the Afro-Caribbean community). A more modern metric is that London is England’s gayest region. Though under 4% of its people identify as gay, lesbian or bisexual, where sexual orientation is known, men who have sex with other men account for half of its new STIs.

Such figures are in part a sign of liberation. HIV is no longer the death sentence it was for many in the 1980s. Pre-exposure prophylaxis (PrEP), a pill taken daily, can almost completely ward it off. According to Preventx, a testing firm, rates of gonorrhoea and chlamydia among men who take PrEP are nearly double those among men who do not, perhaps in part because they feel it is safe not to use condoms. Dating apps (notably Grindr) have made both sex and drugs easier to find. Surveys suggest that around one in five gay or bisexual men in London have sex while on drugs like crystal meth, which can reduce inhibitions and increase sex drive. “You can have a ridiculous amount of sexual partners, upwards of 20 in a weekend,” says Ian, who spent many years having “chemsex”.

The fun is not without risk. Gonorrhoea is becoming increasingly resistant to antibiotics. As well as STIs, “chemsex” carries a greater risk of sexual assault, drug addiction and death. “We probably have more young men dying of chemsex than we do dying of AIDS,” says Dr Anatole Menon-Johansson of Brook, a sexual-health charity.