Swimming is a fingertip sport with wins measured in hundredths of seconds. When Adam Peaty is on form though, the margins are much wider. Peaty is one of those rare athletes who has redefined what’s possible in his event. He was the first man in history to swim the 100m breaststroke in under 58 seconds and is still the only man in history to swim it in under 57. He owns every one of the 10 fastest times in history, and 17 of the top 20. It so happens that the swimmer who owns the other three, Qin Haiyang, is the man Peaty needs to beat in Paris if he is going to become the second male swimmer to win the same event at three consecutive Games. The other was Michael Phelps.

You can talk about Peaty’s size 12 feet, his 38cm biceps, and 117cm chest, you can talk about his high stroke rate, passive glide time, his propulsive kick, and his quick recovery, and you can talk about his competitive streak, which is absolutely pitiless. But according to Bill Furniss, the head coach of British Swimming, if you really want to know what makes Peaty such an extraordinary athlete, you have to start with his work ethic. Now, no one gets to be an Olympian without one of those, but Furniss says Peaty’s is something else. Furniss has been an elite coach for 30 years, and never seen, or heard of, anything quite like it.

“I’ve worked with a lot of high performance athletes,” Furniss says, “and they will all say: ‘I want to win the Olympics.’ Well, if you want to do that, then you have to pay the price. And some of them aren’t willing to do it. They’ll pay it for a short period of time, but they won’t do it every day, day after day, week after week, year after year. Adam will. People see the 56 seconds that he’s racing on TV, but they don’t see what’s behind it, what’s required every day to get to that level and stay there. I have never seen a swimmer, or any athlete, who’s prepared to hurt themselves the way he does in pursuit of being world class in his sport.”

It’s not about the hours, Furniss explains, but how Peaty uses them. “He is utterly meticulous. Nothing’s ever good enough. He’s been quite open about the pressure that puts on him, but if you’re trying to be the best in the world every single second, you just can’t ever take your foot off the gas. As soon as you’ve ticked off one thing, you have to start looking for the next improvement.”

Technically, all this work shows in his stroke. Peaty takes more of them in 50m than most of his rivals, but because he is so quick through his recovery phase (the bit in which he resets for the next pull and kick) he spends more time gliding than them too. Which means he gets more propulsion than anyone else, but is more hydrodynamic.

He has the training, he has the technique, and finally he has the temperament. “If you watch the very best performers in any sport, they grow in the arena, almost like they need that, the big stage,” says Furniss. “They need it to be challenging, because it brings the best out of them. A lot of people can’t handle that pressure. But Adam’s certainly someone who can. The bigger the challenge, the more gladiatorial he becomes. He gives his rivals absolutely nothing, no quarter asked and none given. And you have to understand that swimming at the Olympics isn’t like other sports. If you play tennis, for instance, you’ve also got a chance to win four majors in a year. Adam gets three chances in 10 years. That’s it.”

He’s taken two of them. If he can take the third too, it would be his finest achievement yet after his very public problems with his mental health. “What he’s trying to do is almost unique in the sport,” says Furniss. “The struggles he’s had would have beaten most people, but they haven’t beaten him. To go through all that, and put himself in this position again, is testament to his mental strength. A lot of people would just have walked away and said: ‘You know, I’m not doing this.’ But not Adam. He’s got the gold medals, he’s got the world records, he’s already taken his event to a new level, and no one can take that away from him. But he’s doing it again, for himself.”