Rio found an easy way to boost the attendance at athletics: unleash Usain Bolt. The No 1 star in world sport brought the Olympic Stadium to life after an ominously poor turn-out on Friday. And that was just for his 100m first-round heat, which he won in an ambulatory 10.07 seconds despite feeling “kind of slow.”

This arena, which had seemed so lifeless on Friday, erupted in cheers as Bolt appeared for Heat 7. Even his warm-up jog drew squeals. Halfway down the track he applauded his audience. So they chanted his name as if he were a Brazilian No 10. Back at the start Bolt spread his arms to receive their adoration and gave them the easy win they craved. Then many headed for the exits before the eighth and final heat could be run.

So Bolt’s power to mesmerize is on full show again as he defends his triple crown of 100m, 200m and 4x100m titles for a third straight Games. Rio, you can be sure, is his kind of town, though he was no less in tune with his admirers in London four years ago. His personality casts a spell over crowds and his invincibility at championships feels like the world’s greatest live theatre, even if it lasts less than 10 seconds, and is clouded by doubt about his sport.

Bolt played down this opening display. "It wasn't the best start. I felt kind of slow,” he said. “I'm not used to running this early at any championship. Hopefully tomorrow I'll come out and I'll feel much better, much smoother."

In boxing they used to say you need a black hat fighter and a white hat fighter to really sell a big bout: a good guy and a baddie. In the public’s view the Olympic 100m will deliver that promoter’s dream again when Bolt confronts Justin Gatlin on the start line in Rio. Not only Gatlin, of course, but the next wave, such as America’s Trayvon Bromell. France’s Jimmy Vicaut, though, who had run 9.86 this season, looked to be in physical difficulty in Heat 4 and failed to make the semi-finals. Vicaut has a habit of flaming out in championships.

Gatlin, who has served two doping suspensions, but is somehow still a major player at the age of 34, must have a colossal mental block about Bolt’s habit of starting slowly but then gliding past the field in the final 20 metres.

Again and again Gatlin arrives at major championships running faster than the double Olympic champion. This season Gatlin has run 9.80secs compared to Bolt’s 9.88 secs. But who do you think will be psychologically and athletically tougher when the gun goes for the final?

Gatlin was superbly rhythmic in winning his own first-round heat here in 10.01 seconds, and said afterwards: “The crowd was great. It's the culture [in Rio] to party. It's excitement. We're going to bring that to the track.

“ I felt good. I think I'm going to have to run a bit faster [than his season’s best of 9.80 secs] to win this medal.”

At the World Championships in Beijing last year the Bolt-Gatlin duel was even framed as a battle to save athletics. That was before a vast corruption scandal stretching to the top of the IAAF, and the casting out of Russia for running a state doping programme.

Against the backdrop of governing body and state corruption, the dishonesty of individual athletes loses some of its capacity to shock. Gatlin’s first doping ban in 2001 was for a drug he claimed had helped treat attention deficit disorder; his second, in 2006 was for excessive testosterone, which he blamed on sabotage by a therapist. "It's hurtful, it's hurtful to be looked at as a villain because that's not how I portray myself, that's not how my son portrays me or my family," Gatlin says.

Bolt meanwhile had already left a favourable mark on Rio, with his dance on stage with women dressed for a carnival. His parents have made the news too. His mother, Jennifer, took the Bolt story right back to the womb, telling reporters: "After three weeks he was pushing because he was so strong.” From his earliest days, she recalled: "One day, I left him on the bed and when I came back he was close to falling off, so from here I was saying - what kind of child is he?"

His father Wellesley joined in: "He's upbeat because he said it will be his last Olympics and he wants to go out in a glory, so you can expect great things from him.”

Jennifer Bolt tried to imagine the world of sprinting without him – a scenario the benighted sport of athletics can hardly bare to imagine. "I would like him to be ambassador of track and field because he will put a little more fun into the sport," Jennifer Bolt said. "Without him it will be really boring." Bolt’s mother says he is unchanged by the fame that has enveloped him since the Beijing Games of 2008. "I haven't seen any difference in him because from the beginning, I think his personality is just the same," she said.

Her son has made her a promise, which could bring more agony for Gatlin – the embodiment of leniency towards convicted cheats. Jennifer Bolt said: "He said to us, 'Mom, you know, if I wasn't ready, I wouldn't be here, because you know I'm not in the losing team.'" Rio is on his side.