This article was amended on Thursday November 20 2008

A sentence has been removed. Furthermore, we apologise to Betsy Andreu for comments made about her in this interview. She has asked us to clarify that, while evidence that she gave in proceedings about an insurance claim brought by Lance Armstrong is disputed, she honestly recounted what she believed she had heard.

The sweat is still drying on Lance Armstrong's gaunt face when, with sunken eyes as blue as the cloudless sky, he sweeps through the front door of his home in the secluded hills of Austin, Texas. Armstrong offers a hand while balancing a pile of training gear on his arms. "Sorry, I'm late," he says. "It's been a busy day."

He disappears as quickly as he arrived and I slide back on to the plush sofa of the vast room where I've been waiting. Huge paintings of minimalist pop art hang on the walls. Ed Ruscha's Speed Racer and Safe and Effective Medication echo the backdrop of cycling, cancer and doping allegations which have made Armstrong one of the world's most famous but controversial sportsmen.

An elegant woman drifts past to check whether I need another sparkling water. The temptation is to mumble that a definitive dollop of truth would suffice for no other athlete divides the planet like Armstrong. He could be the greatest sportsman of all time, an epic and courageous figure who overcame cancer to win seven straight Tour de France titles from 1999 to 2005. In the alternate view, however, he simply cheated his way to victory with performance-enhancing drugs.

The ferocious split between believers and critics was illustrated when I canvassed the experts before arriving in Austin. I barely had to mention Armstrong's name to be assailed by a furious response from European journalists who had covered his exploits for years. "Horror-show" and "disgrace" were two of the milder terms of denigration. And yet, interviewing Bradley Wiggins in September, I was taken aback by the Olympic champion's delight just a few days after Armstrong announced his comeback. Wiggins, whose vehement stance against doping has long been enshrined, appeared an unlikely ally of Armstrong. So who do you believe? A maverick racer like Wiggins or a coterie of specialist reporters?

"I don't care who you believe," Armstrong drawls. We sit at a big round table, in touching distance of his seven blue Tour titles on the bookshelf, while Armstrong hunches over a bowl of soup and a cup of green tea. "I understand people in France and in cycling might have that perception but the reality is that there's nothing there. The level of scrutiny I've had throughout my career from the press and the anti-doping authorities is unmatched. I'm not afraid of anything. I've got nothing to hide. There are seven cups in this room because of my hard work. This next year won't be any different - even if people hate to hear that. I'm going to be focusing on every aspect of the bike, the team, the strategy, the training, the hard work, the sacrifice. There are no secrets. To the critics I would say, believe it or not, there are exceptional athletes out there. Michael Phelps ... Paula Radcliffe ..."

But neither Phelps nor Radcliffe has been engulfed by swaths of circumstantial evidence, or links to proven drug cheats. "There has been a fair amount of suspicion around me, and a hell of a lot of suspicion around cycling. If the guys who finished second, third and fourth behind Phelps were all busted then people would say, 'Hey, wait a minute. He beat 'em all - how the hell is that possible?'"

Armstrong nods meaningfully, conceding why there are such doubts about him. The last time he stood on the podium in Paris, in 2005, he said he felt "sorry" for all the poor saps who doubted him and the integrity of the Tour. And yet the two men who shared his podium were both exposed as dopers. What did he think when Ivan Basso and Jan Ullrich were busted?

"Egg on my face," Armstrong says softly. "But look at the Brits on the track this year - absolutely outstanding. And still the head of French cycling said their performance 'is not possible'. Give me a break. Bradley Wiggins is the best fucking pursuiter of all time. I don't think he cheated. So if I could talk to your cycling buddies I would say, 'Just fucking relax. We're not talking about God. We're not talking about war. We're not talking about you losing every dime you had. We're talking about bike-racing'."

Yet we are talking about doping. Three years ago L'Equipe published their claim that a sample of Armstrong's urine from the 1999 Tour had been retested and found to contain traces of EPO. They published their apparent exposé under a banner headline of "The Armstrong Lie". "I remember the call. This house was still under construction and I was in the backyard with the contractor. At the time I thought, 'OK, whatever' - even if it was a big 'whatever'. There was hysteria and they got this big independent commission to investigate.

"Cycling, like the world, is very divided. One side finally said, 'OK, the independent commission cleared him so we're moving on'. The other side said, 'I don't believe the independent commission'. But the report was very clear and we were ready to go to the international tribunal with the lab, with Wada [the World Anti-Doping Agency] and the French government - and they declined. Now they come back and say 'OK, we'll now let you test those samples to prove your innocence'."

Armstrong pushes his cup towards me. "Here's your sample," he says, "and the lid is now off it. Something might have been put in it and your life, your credibility depends on it, but now I put the lid back on. Now we come and test it. Nobody in their right mind would take that test. The commission cleared me and L'Equipe itself said, 'The athlete in question has no way to defend himself'. I'm all for drug controls but if the athlete cannot defend himself, what kind of kangaroo court is that?"

Setting aside the possibility of tampered evidence Armstrong's first sample contained a residue of EPO - a fact he explains away by arguing that he used a cream for saddle sores during his first Tour win without any knowledge that it included a banned substance. Various other people also claim that he admitted to past doping.

Is Emma O'Reilly, his former physiotherapist on the US Postal team, simply a liar - she claimed that Armstrong had asked her in 1998 to dispose of a bag of syringes containing EPO? "We all know the names. Emma O'Reilly, Steven Swart [his former team-mate who admitted using EPO], David Walsh [the respected Sunday Times journalist and author of LA Confidential: The Secrets of Lance Armstrong] and Prentice Steffen [an ex-professional cyclist who told L'Equipe that "the bad guys, like Armstrong, dope"]. We sued David Walsh in the high court and won. The prosecutor in Paris opened a federal investigation and we were completely cleared. We had another arbitration case in Texas and were vindicated again."

Betsy Andreu, whose husband Frankie raced with Armstrong, claims she heard the cyclist tell doctors treating him for cancer that he had taken performance-enhancing drugs. "Her husband lived, trained and raced with me and he said, under oath, 'I have never seen Lance take performance-enhancing drugs'."

Armstrong's past links with Dr Michele Ferrari, the Italian physician charged with various doping offences, are more damaging. "Yeah - but more was made of that relationship than existed. And I'm not going to kick a family friend out of my life. There are those relationships but look at the real data. Nobody had more scrutiny than me."

As part of his mission to prove himself clean on his return Armstrong will be tested daily by Don Catlin, an independent analyst, who will post his results online. But trouble continues to brew. "I don't want to enter an unsafe situation but you see this stuff coming out of France. There're some aggressive, angry emotions. If you believe what you read my personal safety could be in jeopardy. Cycling is a sport of the open road and spectators are lining that road. I try to believe that people, even if they don't like me, will let the race unfold."

Does he fear being violently attacked on next year's Tour? "Yeah. There're directors of French teams that have encouraged people to take to the streets ... elbow to elbow. It's very emotional and tense."

There is also something compulsive about Armstrong's comeback, which can be seen both in his craving to succeed and the fascination surrounding his tilt against the odds. Comparing his fitness at this stage of the season with past years he insists: "I'm much better physically now. And mentally there is no comparison. I'm far stronger and more motivated. The motivation of 2008 feels like the motivation of 1999. I was back from cancer then. I had the motivation of vengeance because nobody wanted me or believed in me."

Nine years later Armstrong sounds more vulnerable than vengeful. "I have anxiety and insecurity about being 37. Let's not forget I'm the oldest tour winner in modern cycling history and that was four years ago. But that nervousness makes me work even harder. We're doing a training camp in December in Tenerife and another in California with big climbs. Normally I wouldn't smell a mountain until February so I'm starting early."

Armstrong will begin the new year in Australia before he returns for the Tour of California and more racing in France and Switzerland, followed by his debut in the Giro d'Italia. "I regret not riding the Giro before. But their 100th anniversary and starting in Venice and finishing in Rome made it irresistible. That's the beauty of this comeback. You lay out different scenarios in your head. What if you won the Tour again? Or the Giro? Or if you won them both? Or you lost them both? You lay it all out and I'm still up for it."

Armstrong suggests that running marathons led to him agreeing to get back on his bike in the 100-mile Leadville Trail in August, the day his comeback began. "Leadville climbs 12,500 feet and I felt good the first six hours. It was only in the last hour I ran out of fuel because I hadn't done enough miles. But I finished just behind Dave Wiens, a former world champion whose whole season revolves around that race."

For a man who has often said losing is akin to dying, Armstrong looks briefly satisfied with that second place. But, deadly serious on the bike again, and beyond the claim that he is aiming mainly to raise money for his cancer foundation, Armstrong is plainly chasing an eighth Tour victory. "When people have cancer it's black and white - they live and they win. They lose and they die. I take that same mentality into sport - to win. My friends on the team were always quite surprised that I wasn't that excited to win. They'd say: 'Aren't you excited? You just won the Tour de France for the seventh time?' I was 'Yeah, it's pretty cool'. It would have been very different if I had lost. But now if I'm able to win again, any race, it might be different this time round. We'll see."

For more information about the Lance Armstrong Foundation, which unites people fighting cancer and provides practical information and tools for those fighting the disease click here.