Casamento gave Irish trainer Mick Halford his first Group One success when taking the Racing Post Trophy at Doncaster under Frankie Dettori.
Wearing Sheikh Mohammed's colours, Dettori took the lead two furlongs out on the 2-1 favourite, and kept on strongly to hold the Aidan O'Brien-trained Seville.
O'Brien's other runner, Master Of Hounds, was third to complete a clean sweep for the Irish raiders.
Dubawi Gold was quickly to the fore as the field assembled in the middle of the course - apart from Seville who was alone towards the stands side in the early stages.
Casamento, one of the three supplementary entries in the race, took closer order at halfway, and hit the front a quarter of a mile out.
He had to be kept up to his work to win by three-quarters of a length from Seville, with Master Of Hounds another two lengths away third.
Dettori said: 'It was a great performance and I'm delighted for Sheikh Mohammed and Mick, which is his first Group One.
I think he's probably a Derby horse, but we'll wait and see.
He's a lovely horse.'
Halford reported: 'I personally think he might have enough speed for the Guineas, but he's not slow either and stays.'
Dubawi Gold was quickly to the fore as the field assembled in the middle of the course - apart from Seville who was alone towards the stands side in the early stages.
Casamento, one of the three supplementary entries in the race, took closer order at halfway, and hit the front a quarter of a mile out.
He had to be kept up to his work to win by three-quarters of a length from Seville, with Master Of Hounds another two lengths away third.
