Alex Yee was toiling in the 30C midday heat, 14 seconds behind his great rival Hayden Wilde, when a bell rang out on the Pont Alexandre III bridge. It was for the last lap of the men’s ­triathlon and sounded like a death knell for his gold medal hopes. Then he heard four words from a familiar voice that helped to change the course of ­Olympic history.

“Anything can happen, mate,” shouted Alistair Brownlee, the London 2012 and Rio 2016 triathlon champion, and one of the smartest minds in the sport. Those words dug into Yee’s brain as he mined deep into his reserves, absorbed the energy of a raucous crowd and started an extraordinary fightback.

At first it was merely about stemming the bleeding. But over a blisteringly final kilometre, something remarkable happened. Yee began a surge so sudden that it caught Wilde and the TV directors unaware. With 400 metres to go, he rushed past his rival before stretching away to take gold by six seconds in 1hr 43min 33sec.

“It’s all a bit of a blur,” Yee said as he struggled to make sense of what had just happened. “It was one of those mad moments where everything just fell into place. I was in quite a bad place. I was going through a really bad patch. But I didn’t give up.”

It was Brownlee, most of all, who planted the seed of the comeback. “With one lap to go, Alistair said to me: ‘Anything can happen, mate.’ He shouted that out. It definitely was a moment of belief. I wanted to give myself that last chance. It’s pretty special when somebody does that.”

When Yee won a men’s silver medal in Tokyo, he was non-­committal when asked whether he was the man to take over from the Brownlee brothers, Alistair and Jonny, at the top of triathlon. Three years later, however, the 26-year-old finally provided the most emphatic answer.

To make matters worse for Wilde, he had no idea that Yee was closing the gap before holding on for silver ahead of Léo Bergère of France. “It was too loud,” he said. “The whole course I couldn’t hear anything, it was fantas­tic. I was just depleted, I was gone, I was done. I had nothing left and I just had to survive to get to the finish line.”

Just before the start, Yee and Wilde shook hands and shared a quiet word. They used to be roommates when they were rookies on the World Series circuit and had little money between them. It was a classy moment, especially given they were about to slug it out for the biggest prize in their sport.

Soon, though, there was clear sepa­ration between the pair. Yee came out of the 1500m swim in a healthy 15th place, 27sec down. Wilde struggled with the chaos and currents of the Seine and found himself a further 36sec further back.

It left the New Zealander having to expend vital energy on the 40km bike section to join a pack of 32 – which played a part in the ­dramatics that followed. “For five minutes I was at 480 watts, which for me is solid, especially on the flat,” he said. “But if I didn’t surge there, and shoot some ammo, it would have been game over. It probably stung my legs a bit too much.”

It also meant that when Team GB’s Sam Dickinson pushed the pace hard towards the end of the bike leg to ensure that Yee would be in prime position for the transition to the 10km run, Wilde was a little further back.

“We were riding at 60kph – no one is going to come around you at 70kph because the physics just doesn’t work,” Dickinson said. “That was our gameplan and it worked to perfection.”

And then some. Yee started the run 50 metres ahead of Wilde, which appeared to be a huge margin given the Briton was a faster runner than Mo Farah as a teenager and ran the 10,000m for Britain in the European Athletics Championships, aged 20. Wilde, though, had other ideas.

First he made up the gap. Then he turned the screw. Soon there was clear daylight between the pair and by the time there was one lap ­remaining Wilde had stretched his lead to 14sec.

But Wilde was starting to feel the effects of a boiling hot day. As he explained afterwards, he had been getting up at 5am and going to bed at 7pm for the past two months to prepare for an 8am start. And so when the race started at 10.45am because of pollution in the Seine on Tuesday, he wasn’t ready for the extreme heat.

“We’re elite athletes and we have to adjust to the circumstances, like the heat,” he said. “I did feel it in the last kilometre.”

On any other day, Wilde would have clung on and become Olympic champion. But this was no ordinary day. And Yee is no ordinary athlete. Afterwards both men looked spent as they sat down and talked about the pain, magic and madness of what had just unfolded.

“We got a battle that we both deserved,” Wilde said. “It was just everything that we had dreamed of. We might be rivals but we’re really good friends. It’s the Olympic spirit, I guess.”