Dwain Chambers is one of the fastest athletes of all time. That is no exaggeration. He is the fourth fastest British sprinter ever, he holds the European record for both the 60 metre and the 4x100 metre relays. He has won countless medals both indoor and on the track. But for many, he is notorious for one thing only: his use of performance enhancing drugs.

On Tuesday night Chambers gave a remarkably honest and open talk to the Cambridge Union, making plain his motivations, his decisions and ultimately, his regrets for those mistakes which cost him so much of his career.

From the very start, it was apparent that his mistakes are not what Chambers wants to be remembered for. After a delay, Chambers emerged on stage smartly dressed, refined and composed. A video was shown of a young woman, Sadie, who had been helped by the cancer charity Teens Unite, one of two he is patron of. He thanked the Union for agreeing to make a small donation. For Chambers, his charity work keeps things in perspective.

Three quotes were then read out, by Nelson Mandela, Oscar Wilde and Winston Churchill, the latter’s being: “All men make mistakes, but only wise men learn from their mistakes.” The tone was set. He would go on to present himself as the man who regretfully did wrong, has admitted it, and seeks forgiveness. We were told that we will all come to our own conclusions about the sprinter’s actions. By the end of his frank and candid talk, it would be hard to doubt his sincerity.

The talk ran through a series of questions, proposed by his agent, the Barrister Siza Agha, to whom he owes so much for helping him put his career back on track – literally. The questions were prepared, but that said, Chambers, in testament to the image he wants to put across, rarely shied away from answering any, even those coming from the floor. Only when asked about contemporary troubles in athletics was he reluctant to give an answer.

Chambers and Agha quickly went through the beginnings of his career, his fame from a young age and how he dealt with it, and how he missed out on the “normal” things of growing up.

But Chambers was no ordinary young man. He burst onto the international stage as a junior world champion, and then in 1999 he would become the youngest ever recipient of a World Championship medal. At the Sydney Olympics the following year, he would finish fourth in the 100m final.

Though for the highly ambitious Chambers, this wasn’t enough. It became evident that Chambers’ drive and determination, his thirst for success, was ultimately what led to his downfall. After his remarkable Sydney exploits, he describes how he was just not been satisfied by fourth.

“I wanted more, I wanted to know why they were superior.”

It was in America that he would encounter performance enhancing drugs for the first time. Having been drawn by the likes of Remi Korchemny and working with World and Olympic champions, he hoped to close the gap on those above him. And then in his own words, a “the man with [the] brown bag”, Victor Conte, appeared, promising to take him “to number one”.

Chambers openly recounts the taking of the performance enhancers, how he knew deep down that it was wrong, but the influence of those around him, all champions, all doing the same thing, meant it was difficult for him to stop.

“I never realised that once I got on that train, I couldn’t get off. I feared that if I stopped, the others would beat me. The only way I could stop was to get caught.”

And in October 2003, he was.

Chambers describes the memory of it vividly; there was both a  sense of happiness that he was caught, but also shock. “Have you ever had the dream where you’re falling, and then you wake up? I didn’t wake up for 12 years, I kept falling.”

His way back to the top would be a long and arduous one. He describes the uncertainty and antagonism he felt from other athletes, who remained suspicious.

As a result, this led him to try other sports, including American Football and Rugby League, neither of which he particularly enjoyed – he described the latter as the “worst thing ever”.

Chambers made it clear, however, that getting caught was not enough for him to feel at ease with himself. His full admission to the press – he was the only athlete to do so as Agha pointed out early on – was how Chambers felt he could the best achieve this, despite how far it would set back his career.

“I had to be able to look my kids in the eye,” he said. Telling his children, he would later go on to say, was one of the hardest things he’s had to do. Besides, of course, telling his mother.

His appearance at the London Olympic games caused controversy and disquiet from many quarters. But for Chambers, it was the end of a long battle, one that he said if he lost, he would have quit athletics altogether.

“This was the moment I’d been fighting for,” he said. “Just to hear the crowd call my name again, it was the greatest feeling ever.”

For now, Dwain Chambers has his mind set on continuing to race and compete for medals, especially in the wake of his eighth consecutive British indoor title. But for the future, it is clear that he wants to give something back to the sport that gave him a second chance, with coaching and mentoring certainly his consideration.

He wants to make sure that other youngsters don’t make the same mistakes as he did. Mistakes that, for 12 years, “ruined his career.”