Reporter: Charles Wooley
Producer: Danny Keens
They've been pushing their bodies to the limit, training like maniacs for their shot at sporting immortality. Now, in just a week's time, our Olympic athletes will take on the best in the world.
We'd like to think they'll be competing on a level playing field. But the sad fact is, there will always be athletes who are prepared to cheat.
Triple gold medallist Marion Jones caused a massive scandal when she admitted using performance enhancing drugs at the Sydney Games. And nowadays those drugs are even more sophisticated and difficult to detect.
So when London organisers claim these will be the cleanest games ever, Marion isn't convinced. Because with so much at stake, the cheats will always be a few paces ahead.