Imperial Commander, winner of the Cheltenham Gold Cup in 2010, has died of a heart attack at the age of 16.
The horse died at Mount Top Stud in County Antrim, Northern Ireland, where he had been based since being retired four years ago.
The gelding won eight races under rules and more than £700,000 in prize money.
“It’s really sad – 16 is no age and we expected to have him longer,” said Ian Robinson, founder of owners the Our Friends In The North Partnership.
“He’d been showing in Ireland and we were looking forward to seeing him parade at Punchestown in a few weeks.”
Imperial Commander also won the 2008 Paddy Power Gold Cup, when Paddy Brennan rode him for the first time, and they ended that season winning the Ryanair Chase at the Cheltenham festival.
Beaten by Kauto Star in the Betfair Chase and King George, Imperial Commander gained revenge under Brennan in the 2010 Gold Cup at odds of 7/1 – finishing ahead of Denman after Kauto Star fell.
Brennan was also on board when Imperial Commander, aged nine, won the Betfair Chase at Haydock the following season – the horse’s last win.
“When he was produced right he was almost impossible to beat,” added Robinson.
“He was full of himself this morning, he ate up and drank up then he had a heart attack. It was all over quickly. He didn’t suffer, that was the main thing.”
Imperial Commander was pulled up in the 2013 Grand National, his penultimate race.