Three-time Grand National-winning trainer Gordon Elliott has apologised after a photograph emerged of him chatting on the phone while sitting on a dead horse.
The 42-year-old Irishman, who trains two-time Aintree winner Tiger Roll, said he had been waiting to help with the removal of the unnamed horse and had acted without thinking.
Elliott, whose principal owner is Ryanair supremo Michael O'Leary, issued a statement late on Sunday after the photo caused a furore on social media.
"I apologise profoundly for any offence that this photo has caused," he said.
"The photo in question was taken some time ago and occurred after a horse had died of an apparent heart attack on the gallops.
"At what was a sad time, which it is when any horse under my care passes away, my initial reaction was to get the body removed from where it was positioned."
Elliott said he had waved away a member of his staff when it was pointed out he was sitting on the horse's body.
"I was standing over the horse waiting to help with the removal of the body, in the course of which, to my memory I received a call and, without thinking, I sat down to take it," he said.
"Hearing a shout from one of my team, I gestured to wait until I was finished."
The Irish Horseracing Regulatory Board has launched an investigation.
The British Horseracing Authority said it was aware of the "shocking image" and officials were in contact with their Irish counterparts.
O'Leary issued a statement on Monday saying it was a regrettable incident but that he accepted Elliott's "sincere and unreserved apology".
"We accept that the photograph was a grievous but momentary lapse of judgement from Gordon," he said.
"We all make mistakes and what is important is that we learn from them and ensure we do not repeat them."
Elliott is set to send a strong team, including the O'Leary-owned Tiger Roll, to the Cheltenham Festival later this month.