Aidan O’Brien enjoyed a one-two in the Prevagen Breeders’ Cup Juvenile Turf as Unquestionable led home Mountain Bear in the Grade One race.

There was a change of plan when stablemate River Tiber was unable to compete in the contest on veterinary advice, meaning Ryan Moore took the ride on Unquestionable in place of Frankie Dettori.

The former horse was expected to be a contender, but in his absence it was Unquestionable who strode to a decisive success as Mountain Bear was steered to the runner-up spot by Dylan Browne McMonagle.