You are only cheating yourself” is the age-old rationale that stops you trying to get round the rules in sport. But time after time some Olympic competitors have proved that they don't mind standing on a podium and proudly and, with a tear in their eye, cheating themselves up to the eyeballs.

For those of us in the traditional “win it right or not at all” camp, we could console ourselves that the cheats would eventually be outed. How we have danced round our campfires over Ben Johnson, Marion Jones and Dwain Chambers; and how we have felt safe in the knowledge that nothing significant gets past the drugs testers.

Well, human growth hormone has changed that dance for me. Set the target by the BBC's Inside Sport of seeing how easy it would be to cheat for the Beijing Olympics this summer, I set out to target HGH. It helps sportspeople in a variety of ways: builds muscle, helps injuries and increases endurance; and all of that without the nasty side-effects of those steroids. Much of it originates in China - as the American Drug Enforcement Agency can confirm.

It's as easy to buy HGH on the street in the UK as a used car - except cheaper. A few weeks' worth of the stuff would cost about £500. And if you take it now you'd feel the effects right through to the summer.

With steroids, testosterone or beta blockers you have to run the gauntlet of the drugs testers at any moment. Steroids last for weeks in your system. The chances of escaping are not good if you use them a lot. The present test on HGH fielded by the authorities will only detect it up to one day after injection. That's it. One day. To date, although the test has been in use since 2004, it has caught the sum total of zero. No one.

If the UK burglary rates sky-rocketed so much that the Government unveiled a new police weapon to catch the thieves, I would want it to be something a bit more effective than blindfolds for the beat bobbies. But this is essentially what the International Olympic Committee is doing. It is standing by its HGH test and refuses to discuss the detection time period. But cheats are clever. If it took me a few hours to find it all out, how is any of this going to be secret from them?

I have seen first-hand how easy it would be to find, buy and use HGH. I've seen how little you'd have to improve your performance to make the difference between being a finalist and a medal winner, or a medal winner and a champion. I also know just how fantastic the respect is when you can legitimately call yourself Olympic champion. I want that respect to remain the same. But if the holes in the system are this large, then how can it be?

Sir Matthew Pinsent is a four-time Olympic rowing gold-medal winner

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