The 28-year-old Jamaican has shied away from suggestions that he was racing at these International Association of Athletics Federations (IAAF) World Championships as a defender of the sport's values against an American opponent who has been sanctioned twice for doping.

But, in the Stadium where he announced his greatness to the wider world at the Beijing 2008 Olympics, Bolt - whose racing this season has been undermined and delayed by problems with his joints - estimated that his ninth global gold was the toughest so far.

“I definitely think it was my hardest race,” he said after his victory in 9.79sec.

“I’ve been through a lot this season, and Justin has been running fast.

"I knew it wasn’t going to be easy, I’m just happy that I got it done and I’m proud of myself.”

Gatlin, who embraced the Jamaican after finishing second in 9.80, had arrived at the start line as the fastest qualifier in an ominously swift time of 9.77 after Bolt had only just managed to qualify from his semi-final.

With 30m remaining, it was not just the gold that was in doubt for the multiple world and Olympic champion but a place in the final itself as a stumble coming out of the blocks left him chasing four others. He moved past them all in the closing metres, however, even looking inside to them as he crossed the line in 9.96.

“I went to see my coach after the semi-final and he said, ‘You are thinking about it too much’,” Bolt added.

“And he is right because I knew exactly what to do.

"I guess this recipe of confidence will also work for the 200m which is also my favourite event…

"My aim is to be number one until I retire.”

In a final that required nine rather than eight lanes after fastest finishers Jimmy Vicaut of France and home sprinter Bingtian Su could not even be split by a thousandth of a second in the semi-final - both clocking 9.987 - the bronze medal also had to be shared in identical circumstances as 20-year-olds Trayvon Bromell of the United States and Andre De Grasse of Canada were each timed at 9.911.

On a day that began with the IAAF President Elect, Sebastian Coe, presenting Mo Farah with his 10,000m gold medal, another home London 2012 champion, Jessica Ennis-Hill, regained the world heptathlon title she won in 2009 with a solid gold display of competiveness in her first major championships since the last Olympics.

Ennis-Hill’s consistency meant she entered the final 800m event as gold medallist elect, with a cushion of six seconds and no clearly superior opponent ranged against her.

But she, like Bolt, bought it home, overtaking eventual silver medallist Brianne Theisen Eaton, who leads this year’s rankings with 6,808 points in the final straight to win the race and take the gold with a total of 6,669 points.

“This is definitely one of the greatest moments in my career,” said Ennis-Hill.

“To come back and win here in Beijing is amazing.

"To be honest me and my coach didn’t even talk about the gold medal - I didn’t really think about it.

"I thought it would have been a little bit too far out of my reach.”

China’s Zhen Wang matched the previous day’s achievement of team-mate Lijiao Gong in the women’s shot put by taking silver in the 20 kilometres walk after being overhauled by Miguel Angel Lopez in the final kilometre.

The Spaniard won in a personal best of 1 hour 19min 14sec, with the Chinese athlete clocking 1:19:29, describing the victory as “the greatest moment of my life".

Joe Kovacs of the United States won his men’s shot put battle with Germany’s defending champion David Storl, 21.93 metres to 21.74m, while Pawel Fajdek of Poland lived up to his favourite status in the men’s hammer throw with a winning effort of 80.88m.

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