Almost every day for the past 15 years, Ben Proud had to make his whereabouts known to the doping authorities. Travelling for work? His hotel would have to be logged on a clunky website. Staying over at a new girlfriend’s place? That would have to be recorded, too. It didn’t make for the most spontaneous of lives. But it’s what you have to do if you want to be an Olympic athlete. 

In 2024 Proud had won a silver medal in the 50-metre freestyle swim at the Paris Olympics. It had been his third Olympics and the high point of his career. But last November he was in a slump. He was 31, old for a competitive swimmer. His knees hurt and his back was shot. There was a persistent, dull pain in the tendons around his elbows. 

One Wednesday at 6am he heard a knock at the door of his flat in Stratford, in east London. He opened it to find a man and a woman, sent by UK Anti-Doping, Britain’s drug-testing body. They were there to check that Proud was complying with what is known among Olympic athletes as “the Code”, a set of regulations circulated by the World Anti-Doping Agency (WADA) that includes an agreement not to use a list of prohibited substances.