European 400-metres hurdles champion Williams, who was banned for four months, and fellow-Welshman Warburton, who was out of action for six, did not know they had taken a prohibited substance which was found in a contaminated energy drink, it was found. 

The UKAD report said the pair were "victims" but they had "brought this matter on themselves", but accepted their evidence that they had not knowingly taken anything containing the prohibited substances.

In a statement this morning, UKAD Director of Legal Graham Arthur added: "These cases send a powerful reminder to athletes that there is no guarantee that any supplement product is free from banned substances.

"Athletes are strongly advised to be very cautious if they choose to use any supplement product and must undertake thorough research of any products before use.

"Information revealed as a result should be further investigated and we advise athletes to keep evidence of their research.

"The principle of strict liability dictates athletes are responsible for any substance found in their body."

Williams has served a four month doping ban but has been cleared of deliberately cheating ©Getty Images



Williams tested positive at the Glasgow Grand Prix on July 11 last year, while 800m runner Warburton was tested out of competition on June 17.

Failing the tests meant the British duo missed the Commonwealth Games but they can now return to action with immediate effect.

"I have never cried so much as I have the last six months," Williams said.

"It's been devastating for all the people around me.

"I don't want to come across as bitter but my message is: 'If it can happen to me, it can happen to anyone.'"

Warburton, who competed for Britain at London 2012, is also reported as saying he has endured a difficult time whilst being unable to compete.

"The hardest six months of my life, being stopped doing the thing I love," he said.

"But the rules are in place to catch people who are cheating.

"We are responsible for what it is our bodies, I could have had the supplements tested but that costs thousands and I don't earn that much money."

The drink in question, Mountain Fuel Xtreme Energy, was sent to an independent laboratory, which confirmed that it contained anabolic steroid metabolites in its blackcurrant drink.

800-metre runner Warburton's evidence that he was unaware the drink contained a banned substance was accepted by UKAD ©Getty Images



Mountain Fuel chief executive Darren Foote told BBC Wales he was glad both Williams and Warburton would be able to return to competition, claiming he is adamant it was accidental contamination.

"I'm not going to give stuff to them that has anabolic steroids in it," he said.

"I'm just chuffed the guys are back in running.

"I stood by them all the way, I'm glad the truth has come out, they are genuinely 100 per cent good guys."

Williams could have been banned for a period ranging from one to two years but his lawyers successfully argued and got his suspension reduced owing to recent changes in the World Anti-Doping Code.

The National Anti-Doping Panel had said the 30-year-old "had acted with no fault or negligence", and subsequently his ban was shortened as under the new tribunals have a wider discretion upon a finding of no significant fault or negligence in cases concerning contaminated substances.

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