Best Mate's much-anticipated racecourse return ended in tragedy as he suffered a suspected fatal heart attack in the William Hill Haldon Gold Cup at Exeter.
Paul Carberry tracked the leader Ashley Brook for the first half of the race on Henrietta Knight's triple Gold Cup winner but he started to nudge the horse on as the leaders moved clear.
The jockey began to ease him in the home straight, eventually pulling him up, and screens were swiftly put up around him.
Best Mate, owned by Midlander Jim Lewis, had been forced to miss an attempt at a fourth consecutive Gold Cup when he burst a blood vessel in his final workout before the big race.
Knight's husband and assistant Terry Biddlecombe said: "Paul is a good jockey and he knew something was wrong. The only consolation is it was pretty instantaneous and he wouldn't have felt any pain."
More on this story in Wednesday's Birmingham Post