Colin Jackson has stoked up controversy ahead of tomorrow's 100 metres final at the world championships in Canada by claiming it is inevitable that some competitors will have taken drugs.
The world 110m hurdles record holder, who decided not to defend his title in Edmonton, believes up to four of the world's top 20 athletes could have used performance-enhancing but illegal substances.
"In the 100 metres final in Edmonton, out of the eight runners at the start possibly two of them would be taking drugs," he said.
"I would say out of the top 20 or so competitors probably four would be on drugs, but it's very difficult to just look at them and say they are taking drugs."
Two-times world champion Jackson told The Mirror: "People say you can spot signs that someone is taking drugs by looking at things like the colour of their fingertips.
"The only way you really know is if a runner blatantly comes up to you and tells you he is taking drugs, or you know his doctor who tells you what is going on.
"People have approached me throughout my career to tell me that a competitor is on drugs, but none of the runners named has been British." -PA