Top Irish show jumper Cian O'Connor has been stripped of victory at a Grand Prix event in Mexico after his horse Pegasus tested positive for a prohibited substance.

O’Connor and Pegasus had topped the podium at the CSI2 Grand Prix in San Miguel de Allende on October 12th, but a subsequent sample revealed the presence of dexamethasone. The finding placed O’Connor on the International Equestrian Federation’s fast-track sanctions list earlier this week.

Dexamethasone, an anti-inflammatory drug, is permitted outside of competition but is typically forbidden during events.

Despite the ruling, O’Connor will not face a suspension provided he avoids any similar violations in the future.

Addressing the issue in an interview with the Irish Independent, O’Connor said: "I had a totally unexplained medication violation on one of my horses while competing in Mexico over two months ago.

"I have categorically outlined to the FEI that neither I or my staff administered any such medication to the horse."