Medal tally: Phelps with Schooling after the 100 metres butterfly final. Credit:Joe Armao He walked around the pool deck at the Rio Olympic Aquatic Centre gazing up at his idol, still in awe. "Why don't you go four more years?" Schooling asked Phelps as they walked. "No way," Phelps said with a smile. "This is crazy, this is out of this world," Schooling said of the cheers washing over them.

Phelps shared the silver medal with Laszlo Cseh and Chad le Clos. Credit:Getty Images And then, as Schooling told it later, Phelps "just looked at me and said, 'I know.' Just walking alongside him, I'll cherish that for the rest of my life." Schooling only became awestruck after the race. For 50 seconds in the water, he had been an assassin. Having ruled the heats and the semi-final, he dominated the final too, hitting the turn in a clear first place and never ceding an inch. Phelps with a 13-year-old Schooling. He had beaten Phelps in the past, too.

What did count against Schooling was the gap of a mere 22 Olympic gold medals, three of them in this event in Athens, Beijing and London, and the sense of history, power and inevitability that that implied. But Schooling ran - flew - away with the race in a time of 50.39 seconds, faster even than Phelps had swum in winning this event in 2004, 2008 and 2012. Singapore's first Olympic swimming medallist began his journey into the sport in Mandurah, Western Australia, where his great-uncle Lloyd Valberg, who had been Singapore's first-ever Olympic representative as a high-jumper in the London games, lived. Hearing stories about Valberg inspired the young Schooling to announce to his father Colin: "I want to go to the Olympics." Once Schooling's talent became obvious, his parents sent him to board at the Bolles School in the United States, where he trained under fabled coach Sergio Lopez.

"I wasn't the easiest guy to train," Schooling recalled. "I didn't want to be there. I got in a lot of fights. I was .. telling the coach to go get stuffed. He put up with so much from me so I could be here. I give a lot of credit to Sergio." It was while he was a student that Schooling first met Phelps. The moment, captured on camera in 2008, was circulating on social media within minutes of Schooling's win in Rio. "Michael and the US team came ... to the country club that I trained at [in Singapore]. I was trying to do my Chinese essay for school. "Everybody was saying, "It's Michael Phelps!' "I rushed out, wanting to get my picture taken. It was in the morning. When I saw him, I was shell-shocked, I tried to smile but I couldn't even open my mouth. It's crazy what can happen in eight years. I'm honoured and privileged to race alongside him."

Phelps remembered monkeys stealing power bars that the American swimmers left around the country club pool, and Schooling and other pupils showing him the primates from a golf cart. He said he was proud to have inspired children like Schooling to challenge him, even if "I don't enjoy losing". Since those days, Schooling had risen through the Bolles School and then under Eddie Reece at the University of Texas. His win did not come out of the blue. Like Suriname's Anthony Nesty, who upset the great American Matt Biondi in the same event in 1988, Schooling had become an American product, familiar to Phelps, who said: "I've been watching Joe swim for a while, and what he is able to achieve is up to him… I'm excited to see how much faster he goes." Phelps insisted that he will be watching that progress from the sidelines. Having buried Caesar, Schooling was in a rush to praise him.

"Growing up, most swimmers idolised Michael. He's the greatest. One gold medal is nuts, I can't imagine 22 or 23. As a kid, I wanted him to win, and he's the reason I wanted to be a better swimmer." As of now, at this distance, in a thought that shocked and almost horrified him, Joe Schooling from Singapore has become a better swimmer than Phelps himself.