Derby contender Hidden Law suffered a fatal injury after winning the Chester Vase on Wednesday.
The son of Dubawi, trained by Charlie Appleby, broke down soon after passing the finishing line under jockey William Buick
Buick immediately dismounted after the horse took a false step, but he could not be saved.
“He fractured his leg, unfortunately,” said Appleby.
“He passed the line all OK and then when he’s crossed the road, he’s taken a false step on it and he’s come down on it basically.
“It’s one of those very freak accidents.”
Owned by Sheikh Mohammed’s Godolphin team, the 9-4 chance had won the Group Three race, a leading trial for next month’s Derby at Epsom, by three lengths from Agenda.
“I feel so sorry for His Highness Sheikh Mohammed and Team Godolphin. To have a horse like him potentially coming through the ranks was exciting for everybody. It’s a sad day,” added Appleby.
Earlier the Ralph Beckett-trained Forest Fairy (11-4) gave jockey Rossa Ryan his first victory at Chester in the Cheshire Oaks.
