One of Britain’s top athletes in the past decade is facing a storm of suspicion today after it was revealed in The Sunday Times that their blood values had a 1,000-1 chance of being achieved through natural means.

The British newspaper gained access to the document which outlined the blood data of thousands of athletes over an 11-year period, first uncovered by Hajo Seppelt of German TV network ARD, and the information reveals that the athlete in question had, on three occasions in their career, results which were “abnormal” – coded with a red mark against their name, which corresponds to the level of suspicion.

At certain races they ran, the athlete registered the highest abnormal reading among all of their competitors, with results varying by as much as 47 percent.

Though the readings were suspicious, they were not enough to register an anti-doping rule violation at the time because before 2009, such tests were only used to spur target testing for EPO.

In response to the allegations of doping, the athlete said last week that their levels had been elevated due to dehydration after running a race in summer temperatures. “They didn’t come back to me because there isn’t anything to show,” they said.

The athlete’s second abnormal test, years later, did spark an IAAF investigation, but the athlete said 11 out of 12 experts who viewed the data concluded that the reading was consistent with an athlete training at altitude.

Experts agreed that dehydration can affect natural blood values, but the British athlete’s off-sc0re, the measure used to determine if an athlete has blood doped, was 40pc higher on the day of the race compared to two days earlier.

The athlete, who cannot be named due to the inconclusive nature of the evidence and threat of legal action, firmly denied cheating and swore to reporters on the lives of loved ones that they had never blood doped.

“You print it and I sue you [and] you won’t be getting any money back in future like [in the case of] Lance Armstrong – I promise you that,” they said.

The athlete is one of 12 British athletes to have recorded abnormal blood values in the 11 years spanning 2001 and 2012.

Mo Farah, who has endured continued speculation about his performances in the wake of the BBC/ProPublica allegations against his coach Alberto Salazar, was not among the British athletes with abnormal readings in that period, nor was British athletics’ other major star of recent years, Jessica Ennis.