London 2012 Olympics: Oscar Pistorius primed to offer Michael Johnson and critics a swift response "It only concerns me when people say, "Oscar's prosthetics are lighter, therefore he has an advantage." Michael has calculated a lot of variables: what the experts are saying about my legs in terms of tendons, muscles, straight-line running-speed, acceleration, deceleration. He does not disagree with the tests that we have done. There are just certain points that he has an opinion about. The point about Pistorius's legitimacy, or lack of it, as an Olympian is rather crucial, however. For when this charming young man from Johannesburg appears in the Olympic Stadium on Aug 4 for his 400m heat, it promises to be one of the seminal moments of the Games. Paralympians have transferred to the Olympic stage before - not least South African swimmer Natalie du Toit, who lost her left leg aged 16 - but never a double amputee. Ever since Pistorius was born on Nov 22, 1986, without fibulas in either of his legs, his resolve to surmount his disability has been a global cause célèbre. He is not prepared for his greatest accomplishment to be eclipsed by the critics. "These prosthetic legs follow exactly the same model that has been around since 1996," argues Pistorius, whose right to enter able-bodied competitions was endorsed four years ago by the Court of Arbitration for Sport. People say that the technology is futuristic, but it's not. It's made of carbon-fibre, which has been used in prosthetic legs for more than 20 years. Michael knows that the leg I'm using is not a cutting-edge piece of equipment. There isn't a single other Paralympic athlete besides me who has even run under 50 seconds in the 400m using one. For the record, Pistorius's personal best in the 400m is an extraordinary 45.07sec, recorded in Lignano last summer. Let us briefly, but dispassionately, examine the evidence. Pistorius" artificial legs are, to give them their full trade name, Ossür Flex-Foot Cheetahs, a pair of passive elastic springs designed to emulate biological limbs. The decision by the CAS to overrule the International Association of Athletics Federations, who claimed that Pistorius could run at the same speed as able-bodied competitors while using less energy, was unanimous. Similarly, the notion that he could be less susceptible to injury, due to the absence of muscles or joints below the knee, was suspect. Paralympians, sustaining nine injuries in every 1,000 hours of training, are shown to suffer more than non-amputee sprinters, who endure an average of six over the same period. As Aimee Mullins, the American Paralympian who also underwent a double amputation, puts it: "If it was the legs that were making us super-fast, I would have done a decade ago what he is doing now, and so would others. Oscar is not running with any different technology than what I ran with in Atlanta in "96." Pistorius is acutely sensitive to accusations that his mere presence in London threatens to lead his sport into unchartered ethical waters. He walked out of a BBC interview last year when asked if he thought he was an "inconvenient embarrassment" to the authorities. Here, even in the more restful surrounds of Gemona, where the landlady of his hotel has baked him a cake bearing the five Olympic rings, the resentment lingers. You'll find a journalist who has not approached the story properly, or somebody with the title of professor or doctor who wants to make a name for himself. He will argue that water is dry, or that orange used to be green. They will try to be controversial for the sake of it. Flanked by long-time coach Ampie Louw and manager Peet van Zyl, he says: "I read an article that mentioned "our scientists." They were not, they were a group of three people we got together and whose findings we promised to publish. These were not guys who had been sucking their thumbs - they had reputations.They did a whole host of tests, and our results are open for peer review. Honestly, this is not something I can give much more energy to. I would be answering these questions for days. Instead, Pistorius must preserve his intensity for the track. As fortune would have it, the Mayor of Gemona del Friuli is so honoured by the arrival of this celebrated figure that he has built him one. Directly before this interview he has reeled off lap after lap in torrential rain, unrelenting in his quest for the sub-45 second time that he and Louw believe is within reach. But what, in terms of an outcome in London, does he see as attainable? "A decent position in the semi-final," he replies. I wasn't happy with my performance at the World Championships in Daegu. I had an unbelievable race in the heats, but misjudged the semi and finished last. This time I'll have to go flat-out from the start. The stage is far too grand to afford any miscalculations. The arc of the Pistorius narrative, encompassing his first efforts to walk and his astonishing precocity as a sprinter, has all been leading to the Olympic crucible in London. His parents, his brothers, his best friends and even his grandmother will all be at the Olympic Park to savour his history-making display. "I'd like to show people that if you put the hard work in and you believe in yourself, then you can do whatever you want to," he says. "I still find it strange, I suppose, when I say to someone, "Can you just pass me my leg?" But I don't ever think about my disability. Putting on my legs is like putting on my shoes. I understand that's how some people might think differently, but I hope that in London, their perceptions open up. To Johnson and the doubters, there could be no more eloquent riposte.