Usain Bolt wins Olympics 100m final at London 2012

Usain Bolt emphatically confirmed his status as the greatest sprinter in history as he retained his Olympic 100m title in peerless fashion.

Bolt, doubted by many after a season dogged by defeat and injury, ran the second-fastest time ever to beat fellow Jamaican and training partner Yohan Blake into silver and American Justin Gatlin into bronze.

Bolt's 9.63 seconds, just 0.05 seconds slower than his own staggering world record, was a new Olympic best and capped a race in which seven men went under 10 seconds, with only the injured Asafa Powell failing to break that mark.

"I was happy when I went out in the first round, I felt I could do this," said the 25-year-old Bolt. "I was slightly worried about my start. I didn't want to false start again, so I sat in the blocks a little bit.

"It wasn't the best reaction in the world but I executed it and that was the key. My coach said 'stop worrying about the start because the best part of your race is the end'. It worked.

"I said it on the track, people can talk, but when it comes to championships, it is all about business for me - and I brought it."

He also praised the crowd inside the 80,000-capacity Olympic Stadium.

"It was wonderful," he said. "I knew would be like this. I can feel that energy and I am extremely happy."

Bolt had been beaten by Blake at the Jamaican trials in July and clocked his slowest-ever 100m time at senior level earlier in the season.

When he admitted both his back and hamstrings were troubling him and said he was only "95%" fit, there were those who felt he was more vulnerable than at any time since his Olympic gold in a world record four years ago, a feat which took him to the pinnacle of his sport.

If this was 95%, then his world record of 9.58secs, set in Berlin in 2009, could have gone had he been fully fit.

He had been worried all season about his start. But there was to be no repeat of the false start that cost him his world title and aura of invincibility at the 2011 World Championships in Daegu.

His reaction time of 0.165secs was significantly better than that of both Blake and Gatlin, and although former world champion Tyson Gay got out fast, Bolt was into his long stride quickly.

At 40m Gatlin - banned twice for doping offences - held a fractional lead but Bolt, as so many times before, was about to pull away as no other sprinter in history has.

In Beijing he had eased up in the final 15m, punching his chest with delight, but here he went hard to the line and dipped with a grimace.

Blake (9.75secs) and Gatlin (9.79secs) both set new personal bests while Gay's 9.80secs was good enough only for fourth.