Moore had secured his 80th Royal Ascot victory as 7-4 favourite Illinois won the Queen’s Vase from Highbury in a 1-2 for trainer O’Brien.
It was an eighth win in the race for O’Brien, which matches the record of Sir Henry Cecil.
Big-spending owners Wathnan Racing – headed by Sheikh Tamim, the emir of Qatar – bought several horses for Ascot in the build-up to the meeting and struck in Wednesday’s opening Queen Mary Stakes.
The 22-1 chance Leovanni, trained by Karl Burke, stormed clear in the final furlong under James Doyle, with Gavin Cromwell’s 50-1 chance Mighty Eriu in second.
Running Lion (6-1) gave jockey Oisin Murphy his second victory of the 2024 meeting in the Duke Of Cambridge Stakes.
Trainers John and Thady Gosden had the first two home, with the grey winning from stablemate Laurel, who was returning from a 396-day absence.
And Murphy clocked up another as Wild Tiger won the Royal Hunt Cup for Godolphin trainer Saeed bin Suroor.
The 11-2 joint favourite held on by a head from the fast-finishing Sonny Liston, runner-up for the second year running for Ralph Beckett.
But Beckett had immediate compensation in the Kensington Palace Stakes thanks to the well-bred Doha, a son of Sea The Stars and Treve, ridden by Hector Crouch.
