Pat Eddery, 11 times crowned flat racing champion jockey, has died at the age of 63.
Eddery also claimed four Prix de l'Arc de Triomphes and won over 4,600 races before his retirement in 2003.
Confirming the news, Teddy Grimthorpe, racing manager to Prince Khalid Abdullah, in whose silks Eddery had some of his greatest days, said: "It is extremely sad news. Everyone at Juddmonte is very shocked and saddened by it."
Eddery's achievements put him on record as one of the greatest jockeys of all time.
He won 14 British Classics, including three Derbys aboard Grundy (1975), Golden Fleece (1982) and Quest For Fame (1990).
However, his performance aboard Dancing Brave in the 1986 Prix de l'Arc de Triomphe is widely regarded as one of the most memorable of his career.
In one of the classiest fields ever assembled, Eddery made his challenge last, down the centre of the track, to snatch victory.
Other famous successes include those of Pebbles at the Breeders' Cup, Silver Patriarch in the St Leger - which marked his 4,000th winner - and Zafonic in the 2000 Guineas.
Grimthorpe believes Eddery's championship tally was testament to his abilities in a perceived golden era for jockeys.
''He spanned the greatest era for jockeys ever. Lester Piggott, Steve Cauthen, Willie Carson, all were exceptional yet Pat's ability was unquestioned,'' said Grimthorpe.
Eddery, who had been suffering from ill health of late, began a training career following his retirement, with the highlight being the victory of Hearts Of Fire in a Group One in Italy.
Bruce Raymond, a former weighing room colleague, described Eddery as a ''fun guy'' and ''ultra competitive''
''It's very sad. He'd been unwell for a long time. I just knew him as a good, fun guy. Everybody knows he was a great jockey,'' said Raymond.
''We used to play cards and have lots of fun. I can't imagine anyone being in his company and not enjoying it.
''I was with him abroad - Hong Kong, Italy, Germany, everywhere. We travelled together. He was good, fun guy and very generous.
''He was blooming tough to ride against and cool. He was ultra competitive. He would beat you in a photograph and laugh about it afterwards.''