Go Native, Noel Meade's brilliant winner of the 2009 Supreme Novices' Hurdle at Cheltenham, has suffered a fatal fracture to a hind leg during routine exercise at the former champion trainer's Tu Va yard in Co Meath.
A three-time Grade One winner, the nine-year-old had made a stunning comeback in recent weeks after more than two and a half years off with a tendon injury.
He rolled back the years to win on the Flat under Nina Carberry at Galway three weeks ago, before then crashing out at the last flight in last Sunday's Morgiana Hurdle.
The nine-year-old, owned by the Docado syndicate, had just come to lay down a challenge to Hurricane Fly at the time.
Despite the spill, it was a performance that once again thrust him into the picture for top two-mile hurdling honours this term, which makes his loss all the more difficult to stomach for the Meade team.
"His owners and all of us here are heartbroken," a distraught Meade said of the incident.
"Go Native was doing a steady canter when he broke his off-hind leg above the hock. It happened about 100 yards from me and why it happened I do not know.
"He had been 100pc since Punchestown and was hacking through the week before we decided where he might run next.
"It's an awful loss and everyone is gutted. His owners had been so patient and we were all thrilled by how well he came back from such a lay-off. It's terrible, very hard to take. You need to be made of steel in this business."
Go Native earned over €400,000 in prizemoney for his connections.
Boylesports elected to refund ante-post bets on Go Native for this year's Fighting Fifth and the Cheltenham Festival in March.