Athletes who think they can beat the drug testers are fools warned one of the world's foremost experts on drugs in sport yesterday. "Athletes think they can take things and not get caught. They are wrong," said Dr Arne Ljungqvist, chairman of the International Amateur Athletics Federation (IAAF) medical commission and also a member of the International Olympic Committee (IOC) medical commission. "They think they are steps ahead of us. They are not, we are closing the gap," added the Swede.

Speaking in Seville where the world athletics championships are due to begin on Friday, he also cast serious doubts on athletes who claimed they tested positive after taking food supplements.

"That is not an excuse. An athlete is responsible for what he takes. If you don't know what you are taking, don't take it. I hope that that is the message that has got through to athletes," said Ljungqvist.