Jockey Campbell Gillies has died the day before his 22nd birthday after an accident while on holiday in Corfu.
Gillies led Brindisi Breeze to victory in the Albert Bartlett Novices' Hurdle at Cheltenham this year.
The Scotsman, from Haddington, rode primarily for Lucinda Russell.
A statement on trainer Russell's website said: "He was a much-loved, popular and respected member at Arlary House and it is so hard to lose part of our 'family'."
Gillies, who had over 50 winners for Russell, won 131 races in Britain. He was also associated with the Willie Amos-trained Lie Forrit.
Brindisi Breeze died last month after being hit by a fuel tanker, having bolted from Russell's yard.
Gillies' most recent ride was on Sunday at Hexham and he had been enjoying his most successful campaign with 38 winners in 2011-12.
Born in East Lothian, Campbell attended the British Racing School.
Speaking on behalf of Gillies' mother Lesley, sister Rita, and brother Finlay, his uncle Rory McNeill said: "The whole family is devastated and trying to come to terms with our loss.
"Campbell was dearly loved by one and all, and this is shown by the tributes to Campbell. We hope that at this time we can be given the space and time to grieve."
Russell added: "We are immensely proud of the achievements of Campbell. It was through his innate ability and talent that he reached great heights as a jockey at such an early age.
"More than that, he had a wonderful charm that I believe came across to everyone who met him and through his media interviews."
Assistant trainer Peter Scudamore added: "His victory at Cheltenham on Brindisi Breeze was the pinnacle of Campbell's career. The race epitomised him as a jockey; his belief and confidence and his innate timing.
"He became one with the horse. This empathy and love of his horses was one of the reasons that he was a truly great jockey."
His brother Finlay plays rugby union for Glasgow Warriors, who said in a statement: "The thoughts of everyone at Glasgow Warriors are with Finlay and his family at this terrible time."
Champion jockey Tony McCoy said: "Very sad news about Campbell Gillies - a very good jockey but an even better bloke. All our thoughts are with his family. RIP."
Cheltenham racecourse tweeted: "Desperate news that jockey Campbell Gillies has died on holiday. Our thoughts are with his family and friends."
Gillies' passing was also lamented by Scotland's First Minister, Alex Salmond, himself a keen racegoer and pundit.
"This is devastating news. Campbell Gillies, at the age of 21, had achieved extraordinary success, highlighted by his victory at this year's Cheltenham Festival on Brindisi Breeze," he said.
"The loss of his outstanding talent is a huge blow, not just to racing but to Scottish sport and our thoughts are with his family and friends at this difficult time."