Al Kazeem produced a tremendous performance to lower the colours of hot favourite Camelot in the Tattersalls Gold Cup at the Curragh.
Roger Charlton's British raider was settled in last place of the four runners, just behind Camelot, as the market leader's stablemate Windsor Palace took them along in single file.
All looked to be going well enough for triple Classic winner Camelot but James Doyle ranged upsides at the quarter-mile pole on the lightly-raced Al Kazeem (9-4) and it soon became apparent he had his rival's measure.
Quickening in great style, Charlton's five-year-old claimed the Group One prize with something in hand. A length and a half was the winning margin for Al Kazeem, who was having just his second start since victory in the Jockey Club Stakes at Newmarket last May.
Charlton said: "He's been a slow maturing horse. Last year he came home with a stress fracture of his pelvis in the Jockey Club Stakes. His work has been really impressive and James said the ground was a bit lively for him there. He's a good horse and he rode him confidently. The plan was to drop in behind Camelot and he rode a good race.
"We can look at all the top races over a mile and a quarter and we also know he stays a mile and a half very well. I'd like to think maybe the Arc at the end of the season. Ascot is an obvious possibility, we've also got the Eclipse - there's lots of lovely races there for him."
Doyle was riding his first winner in Ireland and was recording his second Group One winner after the Charlton-trained Cityscape in Dubai last year.
He added: "All credit to Mr Charlton - he's done a fantastic job with the horse and he's done a fantastic job with me as well. He took me on - I'd never even ridden in a Group One race before and he gave me a massive opportunity in Dubai and it paid off.
"Without people like him I'd probably be doing OK but I wouldn't be here today in these type of races. He's a great boss and a great person to work for. He gives me great confidence. My grand-father is from Monasterevin. He's 75 now and he'll be at home watching. My mother used to train and right from an early age I had ponies and stuff. I started riding out when I was about 12 years of age. I'm 5ft 10, it's not easy but as I've got older I've become more disciplined. I can comfortably do 8st 10 so it's grand."
Aidan O'Brien admitted he has had to tread carefully with Camelot after the horse had surgery for colic late last year, saying: "They say it usually takes six months to get over an anaesthetic as big as he had, so we are taking him along gently. He ran a very good race. Obviously we are disappointed he got beat, but that's the way it is and it's a stepping stone on the way.The plan was to go here and then go to Ascot and I think that is still the plan at the moment."