Local trainer Peter Miller added to his Turf Sprint one-two when landing the TwinSpires Breeders' Cup Sprint at Del Mar with Roy H.
Kent Desormeaux had to battle for position just off the pace in the early stages, but Miller's charge really got rolling in the home straight.
Imperial Hint was always to the fore and still led in the home stretch, but Roy H was unstoppable, cutting down the leader to win going away.
Miller said: "I'm so happy, the team has done so well with Roy. Kent rode a great race."
Desormeaux added: "I've got to be really thankful to the southern California horsemen, I'm having one of my best seasons.
"Peter Miller is incredible and riding this horse is like riding an old pony.
"It was a real horse race for about an eighth of a mile in the stretch, but Roy was able to gain the ascendency.
"I couldn't wait to ride him from the first time I breezed him. Thanks to Peter Miller for letting me ride."
Bob Baffert's Drefong was sent off a hot favourite, but he tried to jink out after the start and was never at the races after that.