Gillies, who was also associated with the Willie Amos-trained Lie Forrit, primarily rode for Perth handler Lucinda Russell after joining her team in 2007.

Gillies’ agent Paul Brierley said: “At the present time, all I can say is there has been an accident.”

Campbell's brother Finlay plays for rugby side Glasgow Warriors.

The club said in a statement: “Glasgow Warriors are deeply saddened to learn of the sad passing of Campbell Gillies, brother of Warriors hooker Finlay.

“A promising young jockey, Campbell shot to prominence when he rode Brindisi Breeze to victory in the Albert Bartlett Novices’ Hurdle on Gold Cup day at this year’s Cheltenham Festival.

“The thoughts of everyone at Glasgow Warriors are with Finlay and his family at this terrible time.”

Racing personalities were quick to pay their respects to the 21-year-old Gillies on Twitter.

Former jockey and Racing UK presenter Niall Hannity tweeted: “Devastating news coming through that Campbell Gillies has lost his life in a accident whilst on holiday, thoughts with his family. RIP”.

Gold Cup-winning jockey Paddy Brennan said: “The worst news you cud possibly hear. Campbell you will be sadly missed by us all. Great jockey & even better bloke £RIP.”

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.”

Sam Twiston-Davies said: “R.I.P @campbellgillies class rider and a great person. Will be very much missed.”

His younger brother Willy said: “RIP @campbellgillies, devastating news.”

Brendan Powell jnr tweeted: “Can’t believe it, RIP @campbellgillies, great rider but also a great person, will be a huge loss.”

His father, trainer Brendan Powell, said: “Really sad news about Campbell Gillies. Thoughts are with his family, friends, Scu and Lucinda.”

Grand National-winning jockey Barry Geraghty said: “Very sad news about Campbell Gillies, a very good rider & a lovely fella. He will be sadly missed. All our thoughts are with his family RIP.”

Trainer Gordon Elliot said: “In complete shock to hear the awful news about Campbell Gillies, my thoughts go to his family and friends.”

Cheltenham racecourse, where Gillies enjoyed his biggest success in March, tweeted: “Desperate news that jockey C Gillies has died on holiday. Our thoughts are with his family & friends.”

While trainer Donald McCain said: “Shocking news about Campbell Gillies, thoughts are with all his family.”

Gold Cup winner Sam Thomas said: “Saddening news about Campbell Gillies, a great pilot, a top guy and most of all a true gentleman. My thoughts go out to all his family.”

Trainer Evan Williams said: “Tragic news about Campbell Gillies, thoughts are with his family & friends.”

Jockey Robert Thornton said: “I don’t know what to say. Very, very sad words on here do not do it justice. £legend.”