The mystery of Boxing Day winner Elfhelm's positive drug test has been revealed - he helped himself to a stablemate's drug-laced breakfast. Surveillance tapes showed Elfhelm being led along a corridor of trainer Ricky Yiu Poon-fie's stables at Sha Tin when he put his head in the feed bin of his stablemate, Bite My Dust. Bite My Dust had been prescribed the anti-inflammatory phenylbutazone, which is usually given orally, but because he resisted oral medications stable staff found it more efficacious to add the drug to the horse's feed. When Elfhelm helped himself to some of Bite My Dust's feed, he also took a portion of the phenylbutazone. And that cost Yiu a HK$75,000 fine yesterday. Yiu pleaded guilty under Rule 140(1) for his duty as trainer to ensure Elfhelm raced drug-free when he won the Mount Parker Handicap on December 26, despite the unusual circumstances of yesterday's case. Chief Jockey Club chemist Terence Wan See-ming gave evidence that the level of the anti-inflammatory in Elfhelm's samples was lower than would have been the result of a deliberate administration of the drug. Like all winners, Elfhelm had blood and urine samples taken post-race, and Wan later reported the post-race urine sample had shown the presence of phenylbutazone and its metabolites, gamma-hydroxyphenylbutazone and oxyphenbutazone, and that the post-race blood sample also contained phenylbutazone. Those results were at odds with Elfhelm's race-morning urine sample, taken in the early hours of December 26, some 11 hours prior to racing, and which proved negative for any prohibited substance. Having established the reasonable conclusion that Elfhelm had been exposed to phenylbutazone during that 11-hour period, stewards then viewed security videotapes of the Yiu's stabling area where Elfhelm is housed. And the horse was caught red-handed. Elfhelm was also automatically disqualified as the winner and runner-up Sunny Riviera will now assume the winner's spot.