Treasure Beach continued the good run of form for Aidan O'Brien and Ryan Moore by lifting the MBNA Chester Vase on the Roodee.
Following up the victories of Wonder Of Wonders in the Cheshire Oaks and Await The Dawn in the Huxley Stakes, the Galileo colt held off the late lunge of the favourite Nathaniel.
Sent off at 7-2, Treasure Beach looked to be struggling behind Sadler's Risk as the field turned into the short straight, with Nathaniel looking well beaten at that stage.
To his credit, the 6-4 favourite found plenty when in the clear, but Moore was in the perfect place to take advantage and struck by a head. Treasure Beach was last seen finishing 11 lengths behind Frankel in the Royal Lodge at Ascot.
Moore said: "I had a nice spot round there. They went very steady early on and he travelled very well in behind them. When he got half a gap he quickened up very well and when he got to the front he probably eased up a bit. He'll have to improve to be a Derby horse."
Paul Smith, representing Treasure Beach's owners, said: "I have spoken to Aidan and he was delighted with that. As for the future, the two possibilities at the moment would be the Derby and Royal Ascot because he stays well. That was a good education round a tight, turning track."
Dr Marwan Koukash attempts to have a runner in every race at the meeting if possible and he finally celebrated his first winner in the Irish Stallion Farms EBF Maiden Stakes.
Gabrial, a newcomer representing the irresistible combination of Richard Fahey and Paul Hanagan, was one of two challengers from the Liverpool-based businessman, who has a love affair with the Roodee.
Gabrial forged two and a half lengths away from his fellow 5-2 joint-favourite Sea Odyssey.
Fahey said: "Dr Marwan loves this place and I'm delighted to get him a winner. It's very difficult to work out the two-year-old colts, but he's quite a nice horse."