A father and son who injected what they hoped would be performance-enhancing drugs into their runner before the Foxhunter Chase at Cheltenham on Gold Cup day in March were banned from racing for three years at a British Horseracing Authority disciplinary hearing in London.

Stephen McConville, the trainer of Anseanachai Cliste, and his son Michael, who was due to ride the 33-1 outsider at Cheltenham, injected the horse with Hemo 15, a compound containing the banned substance cobalt, and also adrenaline, about seven hours before Anseanachai Cliste was due to line up for the Foxhunter on 17 March. However, the gelding was scratched from the race on the orders of the stewards after bloodied syringes and empty medication bottles were found during a random search of their bag by BHA integrity officers.

Anseanachai Cliste won a valuable race at Down Royal in Northern Ireland, which falls under the jurisdiction of the Irish Turf Club, nine days after his enforced withdrawal at Cheltenham. A dope test after that success was negative but within days a positive result for cobalt was confirmed from a sample taken on 17 March.

The details of the case which emerged at Tuesday’s hearing revealed a crude and ultimately futile attempt to improve Anseanachai Cliste’s performance at Cheltenham. The gelding was the first horse in Britain to test positive for the element cobalt, a substance that has led to a series of high-profile disciplinary cases in Australia, but the disciplinary panel accepted that neither man knew it was present in Hemo 15, and that a single dose would not have had any positive effect on Anseanachai Cliste’s performance.

The McConvilles administered adrenaline via the drug Adrenal Cortex. It is described as “a potent anti-inflammatory providing some analgesia along with a sense of euphoria” to a horse, but its “duration of action is very short” and any effect would have worn off long before Anseanachai Cliste reached the start.

Stephen and Michael McConville were at the hearing but did not give oral evidence, depending instead on written submissions which largely admitted their breach of the anti-doping rules. In mitigation, both men said that they had not been seeking to boost Anseanachai Cliste’s performance but had administered what they hoped would be a “vitamin boost” after their horse had a difficult journey to Cheltenham.

However, Tim Naylor, presenting the case on behalf of the BHA, said the McConvilles had acted with the intention of improving their horse’s chance, using drugs that had been prescribed several weeks earlier for a different horse in their yard. Naylor also highlighted the chance that Anseanachai Cliste’s welfare would be compromised by the clandestine administration of a drug that had not been prescribed for the horse by a vet, and without full knowledge of what it contained.

Tim Charlton, the panel’s chairman, told the McConvilles that while they “did not have any real understanding” of the substances they were injecting, they “did have a genuine belief these would be beneficial to their horse in a race due to be run in seven hours”.

Charlton continued: “The real vice of what they did was to act in a deliberate and planned way on a race day with the administration of substances and the welfare risks. There was an element of premeditation in that they brought from Northern Ireland [drugs] prescribed for another horse three months earlier, with the intention, or option, of using them.”

In a statement issued after the hearing, the BHA said: “While research surveys and regulatory analysis carried out in recent years were reassuring that there was no endemic issue with the use of cobalt at the time, it is an integrity and welfare threat that we are taking seriously and which is forming an important part of our anti-doping strategy.”

Robin Mounsey, the BHA’s head of media, also addressed the possibility that adrenaline could be administered to a horse in a racecourse stable shortly before it competes. “At the major festivals, most trainers will have their bags and boxes searched,” Mounsey said. “At routine race meetings, the target is one in six trainers having bags and boxes searched but in reality we are probably searching much more than that.”

In a joint statement after the hearing, Stephen and Michael McConville said: “We apologise for what has happened, which was of our own doing due to lack of knowledge. However, this is no excuse for what happened at Cheltenham.

“The horse was administered the tonic, Hemo 15, which is a widely used nutritional supplement which, unknown to us, contained cobalt. We now just wish to put this unfortunate matter behind us as it has caused a lot of stress to all members of our family as the horses and point-to-pointing is purely a hobby for the family.”

Dr Lynn Hillyer, the Irish Turf Club’s chief veterinary officer and head of anti-doping, said on Tuesday evening that Hemo 15 is “a vitamin treatment which is not necessarily regarded as a medicine. It does have cobalt in it [but] there’s not much in it at all and as with all these things, it is about the dose that you give the horse and the timing of that administration. If you give a small amount very close to a race, then it risks exceeding the threshold.

“When we put the thresholds in earlier this year in April, we accompanied it with an advice note to trainers to try to make this clear. A lot of supplements that are given can contain cobalt, so the small print has to be checked, and sometimes the estimations of cobalt given on the outside can be misleading.

“It really is a question of trainers checking with their vets, looking at the label carefully and being very aware of what they’re giving. A lot of these things will have a label on which says ‘Jockey Club approved’ or ‘Turf Club approved’ or whatever else, and no regulatory authority approves any of it.”