"This will be the moment, and this will be the year, when I set myself apart from other athletes in the world," Usain Bolt says in a quiet but dramatic statement of intent on the brink of the Olympic Games in London. The world's fastest man talks with unusually deep concentration, and a calm seriousness of purpose, as he stresses his belief that he will seal his dizzying legacy in the coming days.

"A lot of legends, a lot of people, have come before me," Bolt says. "But this is my time."

There is composure, rather than arrogance, in Bolt's voice. In a candid and open interview, the 25-year-old Jamaican has already dealt with the shadows of his recent dips and doubts and the threatening figure of his friend, and now imposing rival, Yohan Blake. Bolt knows that if he can overcome all his new challenges, and disappointments over the last year, he can join sport's most exalted pantheon.

No man has ever successfully defended his 100m Olympic and 200m titles on the track. Carl Lewis's name is now in the record books after his second-place finish to Ben Johnson in the 1988 Olympic 100m final in Seoul was upgraded to a gold medal following the doping scandal which ruined that race forever. But no sprinter has retained his 200m Olympic crown – let alone repeated a hat-trick by also winning the 4x100m relay for a second successive time. If Bolt replicates his feats from the Beijing Olympics, where he won three gold medals with blistering speed and irresistible panache, his name will echo alongside near mythic sporting figures like Jesse Owens, Muhammad Ali, Pele and Michael Phelps.

In 2008, three billion people, apparently, watched Bolt shatter the world record and win the Olympic 100m final with ridiculous ease in Beijing. His blurring 6ft 5in frame, and huge stride, helped produce the most exhilarating trick of time. Running faster than any man had ever run before, Bolt was so far ahead of his straining rivals he made it appear as if he had slowed to a saunter as he spread his arms wide in a "look-at-me" gesture and crossed the winning line. He wore the expression of a man who had conquered the world.

This time, in London, will be different. Bolt could be tested in exacting ways. Yet an even larger global television audience will be entranced by the prospect of him securing his reputation as the greatest sprinter in history.

The mistaken assumption used to be that Bolt simply needed to turn up, mug for the camera with some dance-hall steppin', and then run and win, before reaching for his arrow-shooting victory pose. "What can I do?" he says. "You can only do your work and let people believe what they want. I work my hardest because I know what it takes to be a champion. I know what I want and I'm focused on what I need to do to win."

Yet a contrasting quartet of races now flits across the usually sunny outlook of the brilliant and charismatic Jamaican. Last year, at the world championships in Daegu, South Korea, Bolt lost his 100m title after he was disqualified following a false start. While Bolt cried out in agonised frustration, as he stalked around a confined area behind the track, the re-started race was won by Blake, his club-mate and younger rival.

Two months ago, in late May, Bolt ran the worst 100m of his professional career and recorded a time of 10.04sec in Ostrava, failing to break 10 seconds for the first time in three years. "I had a bad start and had no feeling the whole race," a dejected Bolt told the massed cameras and recorders. "My legs kinda felt dead. I don't know the reason. The first 40 metres were really bad. I never felt the power out of my legs."

Bolt still won that low-key race but, tellingly, he suffered two defeats in three days at the Jamaican trials. On 30 June, he was beaten in the 100m by the 22 year-old Blake, who won in 9.75sec – 0.11sec quicker than Bolt. More shockingly, on 1 July, Blake defeated Bolt in the 200m, a distance over which the Olympic champion had been considered "unbeatable" for years.

These setbacks have deepened an already consuming interest in the men's sprint for the battle between Bolt and Blake adds another dimension to the glamour and thrilling blur of the 100m. Bolt retains his grip on his romantic title as the world's fastest man and his 9.58 record has been unmatched for almost three years, but Blake has won the three races that have mattered most to them over the last 11 months.

Yet, training in Birmingham as he winds down his preparations for London, Bolt remains engagingly uncomplicated. He does not shy away from a single question or seek refuge in evasive self-effacement. Instead, he is honest in underlining a belief that his "ups and downs" will make retaining his three Olympic titles all the sweeter.

"Definitely," Bolt says, reaching for his favourite word. "When you go through a lot it helps because you can say all these things happened for a reason. The key thing to remember is that hard work does pay off. If you put the work in, it will definitely pay off in the long run."

Bolt speaks plainly when suggesting that, after enduring unfamiliar adversity, he has become mentally stronger. "Yeah, definitely. It gets annoying but, after a while, you get used to people making their own comments and just judging you. But I'm always positive. I know what I want. I know what I am capable of. But it makes you stronger when you have to work so hard to get better and you have to go through all these trials. So I don't stress. I just focus on what is necessary."

He sounds convinced he is now in the kind of shape that will ensure his victory in both the 100m and 200m Olympic finals. "Definitely," Bolt says, relishing the familiar punch of that same old word. "Each training session I'm getting better and better. I have no other duties now, no worries, it's all about training, eating and sleeping. I have a lot more time and can put a lot more effort into training. I'm feeling better every day. As long as I'm feeling myself I'm definitely in no doubt I can go to the Olympics and win."

It's easy to believe in Bolt – primarily because of his outrageous speed and ebullient conviction – but today I am utterly persuaded by his willingness to confront some darker moments. It can be heard in his insistence that "it's always good to lose. It wakes you up." This does not sound like a distressed lament.

Yet footage at last year's world championship captured Bolt's angry devastation at being disqualified. Asked if those emotions defined the worst moments of his career Bolt is emphatic: "Yeah, definitely. Without a doubt – because I worked so hard in coming back from injury last season. Everything came together at the right time and for me to squander it explains why I was so upset with myself. At that very moment it felt so bad because I knew I could've won the race."

Surely the one false-start rule seems crazy to Bolt? If it happened in London, and Bolt or Blake was disqualified, it would kill a much-anticipated race not just for the affected athlete but for billions of viewers. "Listen," Bolt says, "rules were made. For me to make a mistake does not now allow me to say we should change that rule. My coach [Glen Mills] always explains that it's not about anticipation. It's about being professional and getting it done and when you're out there you should listen because the starter is the judge and jury. You should just focus on getting the start right."

Bolt has often struggled with his start, for it is the weakest area of his otherwise imperious sprinting pedigree, but does his disqualification in Daegu haunt him? Did it affect his slow starts in Ostrava and at the Jamaican trials?

"No, I don't think so," he says in a measured tone. "Every season, for me, it's like starting from scratch again. Me and my coach sat down and evaluated and talked a lot about this. We've figured out where I have gone wrong and what I need to do to make sure I get a consistent start."

Has he found a method to produce that more consistent start? "Yeah, yeah, definitely. I've actually bought some blocks that we're going to be using at the Olympics and I've been training with them. I will be much more comfortable and much more consistent starting with those blocks at the Olympics."

And yet, right next to him, or just a few lanes away, Blake will hunker down into his own blocks. Was Bolt shocked to suffer successive defeats to Blake? "You can't say it's a shock. For me, it's good to have your eyes opened wide. To have ups and downs so you can really evaluate what you did wrong or what you need to do to get back where you need to be. It was extremely good it happened at the trials so I could refocus."

Was he shaken by his sluggish run in Ostrava where, briefly, he appeared bewildered by his performance? "No. It wasn't really a concern for long. I just knew [Bolt laughs] I wasn't getting enough sleep. All I needed was some sleep and then I felt better. The next day I was back to my normal self."

Some critics suggested Bolt was partying too much, but did defeat rekindle his hunger for success? "My hunger is always there," Bolt says coolly. "Things happen throughout the season that throw you off sometimes but you have to learn from your mistakes. I just need to put things in place to make sure it doesn't happen at the Olympics. I just try and get over it and get my confidence up to a level where I'm comfortable at the Games."

Bolt was not physically at his best, and struggling with a tight hamstring, but he refuses to excuse his successive losses in Jamaica. Great sprinters, after all, require great rivals to lend gravitas to their legacy. Has Blake emerged, just in time, to push Bolt to even more extraordinary heights?

"Well, for me, Yohan is going to be a great athlete and, so far, he has shown the potential to be that great. But I think, definitely, Tyson Gay is one of the fiercest athletes out there."

Bolt has beaten Gay decisively over the years and it seems striking he should name-check the American alongside Blake. Gay himself has stressed that no one can match Bolt's "big-event mentality". This will be Bolt's third Olympics while Blake remains untested in the most brutal sprinting arena. "I wouldn't say it's a big factor," Bolt says of Blake's inexperience, "but it will play a role because to show up in the Olympics is not easy.

"It's not going to be him alone. It's going to be me, Asafa Powell [also from Jamaica], Tyson, Justin Gatlin [the US's 2004 Olympic 100m champion who returned last year from a doping suspension] and all these guys. It's a packed race with top-class athletes so it will be a different level of competition for Yohan. It's going to take a lot of focus. And it's going to cause a lot of stress. It will really test him as an athlete – and as a person overall. We'll see how good he is."

There is no biting cynicism in Bolt's calm statement. Rather, he makes it sound as if he is as intrigued as we are to discover the depth of an opponent known as The Beast. Was Bolt really the first man to give Blake his nickname? "I said it once and people just took it and called him The Beast. I said he's a beast at training so people have now started calling him The Beast."

Does Bolt regret stamping such a fierce alias on his most serious adversary? "No!" he exclaims. "It's a good nickname and he likes it so it doesn't bother me in any way. It doesn't matter."

In a similarly jokey vein, Blake claims to be a better fast bowler than Bolt, who still carries a high self-regard on the cricket pitch. "He plays lots of cricket," Bolt says of Blake, "so he might be in better shape than me. But I was great. I haven't played cricket in a while but I know what I can do.

He also knows what Blake is capable of on the track. Even more than defeat in the trials, or being forced to surrender his world title, another image links Bolt to Blake. It comes from a Diamond League meeting in Brussels last September on a night when Bolt won the 100m in a carefree 9.76. Yet, later, the cameras homed in on a visibly startled Bolt as he watched Blake cross the 200m finish line in 19.26 – the second fastest time in history. Bolt's world record of 19.19 had not been dented but the taller, older and much more illustrious sprinter could not help himself. His hand covered his mouth as if he needed to muffle his astonishment. It seemed a graphic insight into his true feelings about the rising threat of Blake.

The rivalry between the two men is now such that, sharing the same coach in Mills at the Racers Club in Kingston, they train apart. Yet their friendship off the track continues in seemingly untarnished fashion. At the world championships last year, Bolt shared an apartment with Blake and Powell. Will that happen again at the Olympic village?

"Of course," Bolt says. "We're always going to be friends and team-mates. It's being part of a team. You need to be around people so you can laugh and relax. All the seriousness of the track happens when you line up and the starter takes over. For me the important thing is to be relaxed and not worry about anything."

The rest of us can simply savour a 100m final which is being described as, potentially, the race of all races. Bolt himself hardly resists the giddy anticipation of a sprinting showdown on Sunday 5 August. All eight finalists could conceivably run under 10 seconds. "If the weather is great I definitely think it could be the greatest race. We have six guys who, for sure, can run under 9.9 and they should all make the final. So there is no doubt this could go down as the greatest final ever. If the weather is great and things work out then everything is possible – that's my motto."

Such expectation engenders searing tension. Bolt likes to claim his most jubilant moment on the track came when he was just 15 and he won the 100m junior world championships in Kingston. Yet before that race he was so nervous he initially put his shoes on the wrong feet. He chortles at the suggestion that, considering his commitment to Puma, his long-time sponsors, he won't make the same mistake in London. Yet surely even Bolt will struggle to contain his nerves? How will he compose himself the night before and, then, in the last hour and the final moments before he settles in his starting blocks?

"It's always good to have a little bit of nerves. You've just got to deal with it. And I think I'm past being extra-nervous – especially when I feel myself. When I'm myself there is never any worry and, right now, I'm starting to feel better and better in training. The nerves get less and less the better I feel."

Bolt can relish, instead, the prospect of winning three Olympic finals in London which, for him, "couldn't be a better place. It couldn't get bigger than this. There couldn't be nowhere else because London is really like a second Jamaica."

Is it possible that Bolt, Blake and Powell could complete a Jamaican hat-trick of medals in the 100m? "It's going to be interesting," he says with a throaty chuckle. "But I can't call that because I can't say if everybody will be relaxed on the day. But I'm going out there to win. I can't speak for anyone else."

Gatlin and Gay will be intent on ruining that Jamaican rivalry. The former Olympic champion, Gatlin, has regained some of his old speed and ferocious commitment. At a meeting in Zagreb he even seemed to spit into Bolt's lane – a gesture which elicited amusement in the smiling Jamaican.

"I just think that's what he's used to," Bolt says of Gatlin. "He's pretty much an old-school athlete and, back in the day, it was all about intimidation. But for me it wasn't anything. I was really focused."

Does Gatlin actually believe he can intimidate a man who has run the 100m in 9.58sec? Bolt laughs wryly. "I'm not intimidated by Justin Gatlin. I think he has used it on a couple of other athletes but I'm a different person. It won't work with me."

Bolt, instead, can rely on both his staggering reputation and a renewed appetite for hard work to send a shiver down his rivals. Even The Beast has acknowledged that Bolt has put in the long hours to reach near perfect shape for London. "I've definitely worked hard for these Olympics," Bolt says. "Really hard. You have to put a lot behind you and it's all about sacrifice. You must sacrifice a lot."

His wait for the London Olympics to finally open on Friday is not quite over. The quick man considers the slow drag of an English summer and, for a moment, Bolt sounds almost philosophical.

"I think the days are getting even longer, surprisingly," he says with a light laugh as the deceptive nature of time amuses him. "They seem to be moving real slow now. I guess when you want something to start, now, it takes longer. And, definitely, the evenings are even slower."

Bolt, however, seems set on running so fast he will enshrine his legacy in London. "I've been saying this for years," he murmurs as he reiterates his ambition to dominate. On a cool English evening in Birmingham, as the sun fades and Bolt slips away to face down the hours, his words echo again.

"This will be the moment …this will be the year … this is my time."

Those words conjure up an image of Bolt bending time again as he flies across the Olympic track with fresh resolve. He carries the conviction of a man ready to run into the stunned embrace of history.