The club runner who emerged from the pack to finish as top Briton at the 2017 London Marathon has been sanctioned after a metabolite of cocaine was found in a sample he gave at this year’s Belfast Marathon.

Josh Griffiths, 33, has been banned for three months by the Athletics Integrity Unit (AIU) over the presence of benzoylecgonine, a metabolite of cocaine, in a urine sample he gave after running the Belfast City Marathon on May 3.

The ban ran from June 19, when he was provisionally suspended, until September 18, so he has already served it. All his results from May 3 onwards have been disqualified, with any prize money forfeited. Griffiths had finished fourth in Belfast, according to the organisers’ published prize list.

Griffiths was notified of the positive test on June 19 and his B sample confirmed the result in July. He denied ever having used cocaine and put the finding down to inadvertent contamination from an unspecified environmental source. The AIU said he had not established how the substance entered his system but accepted, on the scientific evidence, that any ingestion of cocaine occurred out of competition – before the end of May 2 – and was unrelated to sport performance.

Cocaine is banned only in competition and the rules provide for a three-month ban where an athlete establishes that any use was out of competition and unrelated to sport performance. Griffiths accepted the violation, which relates to the presence of the substance in his sample, and agreed the sanction without a hearing.

The World Anti-Doping Agency and UK Anti-Doping have the right to appeal the decision to the Court of Arbitration for Sport.

Griffiths came to prominence at the 2017 Virgin Money London Marathon. Then a 23-year-old Swansea Harriers club runner from Cross Hands, in Wales, he started just behind the elite field in his first marathon but began passing elite runners from halfway, finishing in 2:14:49 as the fastest British runner in the race. The run earned him a place in the Great Britain team for that summer’s World Championships in London, finishing 39th in the marathon.

He had no coach, planned his own training mileage and was studying for a master’s degree in sports coaching at Cardiff Metropolitan University. His aim that day had been to run 2:16, the Welsh qualifying time for the 2018 Commonwealth Games.

In 2018 he was 15th in the Commonwealth Games marathon on the Gold Coast in Australia and 49th in the World Championships marathon in Oregon in 2022. His marathon best is 2:11:28 from Seville in 2022.