It was a first win in the race for Buick, who had previously been placed six times, and a second success for Appleby following Coroebus in 2022.
“He’s the kind of horse I’ve not known for that long, but I’ve had so much belief in him,” said Buick.
“It was incredible and the race couldn’t have gone any better.”
Buick had settled his mount towards the back of the field with City Of Troy taking the early lead.
The pair moved nicely through the field and went ahead of Rosallion with just over a furlong remaining and he finished strongly to claim a superb win.
City Of Troy was last year’s star two-year-old, prompting O’Brien to describe him at the time as “the best two-year-old I’ve trained”, while joint-owner Michael Tabor likened him to the great Frankel, who won all 14 career races.