Canford Cliffs has retired from racing after fears of a minor injury spreading.
The four-year-old stable star failed to win in the Duel on the Downs contest at Glorious Goodwood last week.
British horse trainer Richard Hannon confirmed that Canford suffered a small injury on the joint, which has caused him to retire from racing.
"He has a bit of a shadow on the joint running into the pastern and that could turn into something nasty - it could turn into a fracture," Uttoxeter Advertiser quotes Hannon as saying.
"He's a perfectly sound horse and I could very nearly go on training him, but under that light, I don't want to do the horse any damage as he's done us so proud. It's a terrible shame - it's heartbreaking, but I don't want to see him end up with a bad injury.
"He now goes off to stud sound. If anything happened to him, I couldn't forgive myself. He's been a fantastic horse for the yard. He's won five Group Ones - you can't do any more than that."
The Thoroughbred racehorse won the Queen Anne Stakes at Royal Ascot in June, beating 13-time Group One winner Goldikova.