James Lawton: Unbeatable. And Usain Bolt's story still has far to run

World's fastest man becomes first to win 100m and 200m twice. So what could he do without his 'bad back'?

Now that he has exhausted the world's capacity to be surprised, Usain Bolt trades on certainty.

He does it more imperiously – and more quickly – than any man in the history of sport and here last night he did it once more as he made still another mark on the Olympics.

He became the first man twice to win the sprint double, adding to his blistering impact in the Bird's Nest stadium in Beijing four years ago with victory in the 200 metres, four days after his Olympic record-breaking 100m triumph.

Last night he didn't break his own world record, finishing 00.13 off the astonishing 19.19 achieved in Berlin three years ago, but that was at no cost to the wonderment he has been creating these last few days when he walks into a stadium that has been filled with something that can only be described as adoration.

He is, of course, an accomplished vaudevillian when he is not being the fastest man on the planet, and once again he interchanged the roles on his way to another shattering performance.

Yohan Blake, his young Jamaican team-mate and training partner, was widely reckoned to be a serious threat coming into these Olympics, but for a second time he felt the overwhelming weight of Bolt's power and speed.

Blake, who beat Bolt twice in the Jamaica trials, finished second in 19.44 against Bolt's 19.32, but there was never a moment when the result was in doubt. Bolt came into the stadium with all his usual languid humour, crossing himself, demanding the assistance of God with a wagging finger, then putting it to his lips to shush the crowd.

There it was yet again: first the now-familiar ritual – and then the unique and irresistible power as he came out of the blocks. He was running in lane 7, with Blake in 4, but there was never a moment when the attention was allowed to switch from the outside where the reigning champion announced once again that this was the place on Earth where no man can seriously challenge his extraordinary position in the landscape of sport.

There was no serious challenge to another display of physical and psychological mastery from the man who announced his separation from the rest of humanity when he brought the Beijing Olympics to a fever of excitement.

Here in London he has been no less majestic but, unfortunately for last night's anticipation of another world record, somewhat less fit.

He confessed later to a physical vulnerability that was never apparent to the naked eye as he led home the young, outgunned pretender Blake and another Jamaican, Warren Weir.

There had been reports from within the camp that he was intent on smashing the world record and Bolt later confirmed that coming out of that great sweep of a bend, with the field stretched behind him, he thought the possibility was feasible, but then he felt some pain in his back.

"I though the world record was possible, I felt confident, but as I came out of the bend I realised I had a back injury. It has not been so easy for me coming here not quite right, but the important thing is that I achieved my main object.

"Part of the legend was to win both the sprints as I did in Beijing; now I think I am some kind of legend. It was important to me coming to London and it has happened and I'm glad. People always doubt a champion but I never doubt myself.

"It was a pity about the record but I eased up when I knew the race was won. I had done what I came to do."

He usually does. Now, as he approaches his 27th birthday, the world moves another to another phase of the legend.

Will he be able to make anything like the same impact in Rio in four years? He says that we will just have to wait and see, but as he once again accepted the rapture of the London fans, it was hard to believe that he will easily surrender his place at the centre of the world.