Group Three-winning sprinter Steps had to be put down after a gallops accident on Wednesday morning, said trainer Roger Varian.
The Newmarket handler said the loss was a "real blow" after the eight-year-old grey won 10 races from 53 starts.
Steps won two Listed races and a rash of big handicaps, including the Portland at Doncaster last September, during which month he also claimed a five-furlong Group Three at Newbury.
The trainer told his website, www.varianstable.com: "Losing Steps is a real blow. I am gutted for his owner, Michael Hill, and for all of the boys and girls in the yard, for whom he was an old favourite.
"He provided us with many memorable afternoons and he was a horse with real character.
"We will miss him greatly."
