Stravagante has been put down after suffering a "freak injury" in the King Edward VII Stakes at Royal Ascot on Friday.
The Sir Michael Stoute-trained three-year-old was favourite under Frankie Dettori, but was pulled up as the horses prepared to enter the final turn.
Dettori dismounted and veterinary surgeons quickly attended to Stravagante. He was transferred to Newmarket Equine Hospital, but couldn't be saved and a unanimous agreement was reached to put him down.
"It is so sad, it's awful, and as always in these situations your heart goes out to those closest to the horse at Sir Michael's yard," Harry Herbert, racing manager of leading owners Al Shaqab, is quoted as saying by PA.
"It was a freak injury to a fore-leg. The vets did everything they could to stabilise him at the racecourse and he was very calm and peaceful.
"They took him to Newmarket to operate on him and sadly his injuries were so bad all the vets involved unanimously agreed that he could not be saved."
Stravagante was favourite for the King Edward VII Stakes following a runaway victory at Epsom earlier in the month.
