Yanworth: Champion Hurdle favourite failed drugs test after Cheltenham race
Champion Hurdle favourite Yanworth failed a drugs test after finishing seventh in the race at Cheltenham in March.
The horse, owned by JP McManus, showed traces of medication which had not cleared his system on race day.
Trainer Alan King will be subject to a disciplinary inquiry on Thursday, with any penalty likely to be a fine.
Yanworth tested positive for the anti-inflammatory triamcinolone acetonide (TCA).
The cortisone substance was used by British Olympic cyclist Sir Bradley Wiggins, who said he took the drug for allergies and respiratory problems after obtaining therapeutic use exemptions (TUEs). Athletes are allowed to use banned substances under TUEs if they have a genuine medical need.
The substance can also be used legally to treat horses, but it must have cleared their system by race days.
The Champion Hurdle was won by second favourite Buveur D'Air, ahead of My Tent Or Yours, in a 1-2 for McManus and trainer Nicky Henderson.
Yanworth ran again at the Grand National meeting in April, when stepped up in distance from two to three miles, and won the Aintree Hurdle. The seven-year-old passed a drugs test after that victory.
McManus' racing manager Frank Berry has declined to comment.
TCA was also found in the system of last year's Cheltenham Festival winner Any Currency, with the horse stripped of his win in the Glenfarclas Chase, although his trainer Martin Keighley was not fined.
It is not the first time one of King's horses has tested positive for TCA, with the trainer fined £1,000 and Midnight Cataria disqualified from second place at Kempton in October 2015 after the drug was detected in her system.
King and the British Horseracing Authority (BHA) agreed the source of the drug was the trainer's vet, who had treated the mare for lameness, with TCA remaining in her system for 52 days when it was anticipated it would have cleared after 21 days.
In 2011, the McManus-owned defending champion Binocular was withdrawn from the Champion Hurdle two days before the race.
On that occasion Henderson asked for a precautionary test which showed the horse still had medication for an allergy in his system and could test positive on the day of the race.
Meanwhile, the BHA has said its inquiry into trainer Stephen McConville is ongoing after one of his horses was ordered to be withdrawn from the Foxhunter Chase at the Cheltenham Festival. Banned substances were allegedly found in the stable of Anseanachai Cliste.