But Conte's demeanour could not hide the explosive allegations that have sent a dagger into the world of sport. They have cast doubt on the integrity of some of the best athletes in the world and some of the most cherished achievements. They have exposed what many long suspected, but could not prove: international sport and athletics are riddled with illegal drugs.

If the Olympic dream - that most tarnished of sporting ideals - has a grave, it is the in studios of ABC News. It died in the early hours of yesterday morning, British time, as Conte's words were broadcast. Conte, owner of San Francisco-based sports nutrition firm Balco, freely admitted to effectively running the biggest illegal steroid and performance-enhancing drugs ring uncovered in sport so far. It was a network so pervasive that sporting history will now need to be rewritten.

'It's almost like what I'm here to tell you right now is that not only is there no Santa Claus, but there's no Easter Bunny or Tooth Fairy either,' he told Bashir on the 20/20 news show. He went on to sum up what his confession meant in six words: 'The Olympic Games are a fraud. The whole history of the games is just full of corruption, cover-up, performance-enhancing drug use. It's not what the world thinks it is.'

That prompted an immediate rush to the barricades by defenders of the Olympics. 'The Games have survived persecution, wars and everything else, and they will survive this,' said Craig Reedie, chairman of the British Olympic Association. 'They are much bigger than any one athlete. That has been proved time and time again.'

But huge damage has been caused. Conte's shocking interview named the great, and the once thought to be good, of Olympic sport and America's twin passions of baseball and American football. He detailed watching sprinting legend Marion Jones, who won three gold medals in the 2000 Sydney Olympics, injecting his steroids into her own body: 'Marion didn't like to inject in the stomach area ... She would do it in her quad, the front part of her leg.'

Jones has emphatically denied ever using any drugs. She has passed lie detectors and never tested positive for drugs, despite giving countless samples. Conte went on to detail how he developed a secret plan, Project World Record, for Jones's husband Tim Montgomery, aimed at using drugs to help him break the coveted 100 metre world sprint record.'I knew that this was the most coveted of all records... so we kind of had a collective dream and I was the mastermind so to speak,' Conte said. Montgomery duly set a new record of 9.78 in Paris in September 2002, which for now still stands as the official world record. He too denies taking banned drugs.

That raises the prospect that many medals, records and other sporting achievements are at best suspect and at worst need to be scrapped. The World Anti-Doping Agency has called for Jones to be stripped of her medals if she is convicted. Reedie backed that call, raising the prospect of a wholesale re-evaluation of medals and records. 'If people are later found to have cheated ... and have had medals presented to them, they may not necessarily get to keep those medals,' he said.

Ironically for Conte, that sounded like a silly idea. After all, he insisted in his interview, drugs had been in sport so long and been used so prevalently that the 'playing field' was still level. It was confirmation of the cynical joke about the Olympics -it was now a race between chemists, not athletes. Montgomery's record, would still be legitimate even if it was won with the help of drugs, Conte said: 'It's not cheating if everybody is doing it. And if you've got the knowledge that that's what everyone is doing, and those are the real rules of the game, then you're not cheating.'

His allegations have finally exploded the myth that drug testing works. Conte said getting round the test was 'like taking candy from a baby'. Under him, Balco was able to distribute a steroid called 'the clear' which could pass undetected through drug tests. Once detected, it led to the downfall of British sprinter Dwain Chambers.

However, some officials say testing has improved. Michele Verroken, former head of anti-doping at UK Sport, said things had got better even though she admitted Conte was right in saying drugs had been around for decades. 'There are Olympic and world records set years ago which athletes now, because drug testing has been much improved, can't get near,' she added.

'Conte's confession comes amid a high-profile court case in which Balco is being prosecuted for selling illegal steroids. It has come at the end of a week of endless leaks from sealed court papers from the case which finger two of America's most beloved baseball players as users of steroids. That has provoked an orgy of recrimination among sports-mad Americans who now believe their most cherished sporting traditions have been exposed as a fraud. Barry Bonds and Jason Giambi are household names, loved for their ability to blast a baseball high into the stands. Now their reputations are shattered.

Conte's accusations have sparked denials from some people he names, but others have admitted that what he has said is true. On the same ABC News programme, US sprinter Kelli White, who has tested positive for drugs, chronicled how Conte helped her train with his steroids: 'He made me believe that if I followed a certain protocol of supplements and different drugs I could become number one in the world.'

There is also the possibility that Balco is just the tip of the iceberg. 'How many other Balcos are there in world sport? It's quite likely that there are others,' said Verroken. The scandal is clearly only just beginning.

The steroid spectrum

Anabolic steroids, of which there are at least 100, are synthetic versions of the male hormone testosterone.

Doctors prescribe anabolic steroids to Aids patients to help slow loss of muscle mass.

Athletes use them illegally to bulk up, build endurance and recover from training.

Side effects include liver damage, heart disease, anxiety and anger.

To find steroid traces in urine, scientists use gas chromatography and mass spectrometry testing. This involves drying the sample, adding chemicals then heating it. However, during this process, Tetrahydrogestrinone (THG) disintegrates and goes undetected.

American scientist Dr Don Catlin invented a new process that identifies THG. The first athlete to fall foul of this new technique was Britain's Dwain Chambers.