New Zealand equestrian Jock Paget is suspended from competition after the horse he rode to victory at the Burghley International Horse Trials in September tested positive for a banned substance.
Clifton Promise was routinely tested following the competition as part of the International Equestrian Federation's strict Equine Clean Sport programme. The test showed traces of the substance Reserpine.
A second horse Clifton Pinot, which is ridden by Paget's Australian trainer Kevin McNabb, also tested positive.
Paget is provisionally suspended from any national or international competition with immediate effect, pending the testing of the B sample and any subsequent hearings.
Clifton Promise is also suspended from competition.
Equestrian Sports New Zealand chief executive Jim Ellis told Morning Report the news has been a bomb-shell for Paget.
"I've spoken to him four or five times over the last 36 hours and clearly Jock was devastated when the news came through," he said.
"(He's) utterly, utterly surprised, can't understand, I mean there's no logic to this particular substance being in the horse's bloodstream."
Mr Ellis says a sedative might keep a horse calm during the dressage phase of a three-day event, but it would not help in the cross country or showjumping phases.
He says the focus is on whether a batch of feed may have been contaminated or if something more sinister might be to blame.
Equestrian Sports New Zealand says Paget has never intentionally administered any prohibited substance.
The organisation and Paget are will provide submissions to the International Equestrian Federation tribunal as needed.