Ninetieth Minute gave the Irish their seventh winner of the Cheltenham Festival as he powered clear in the hands of Paddy Flood to win the Coral Cup.
The Tom Taaffe-trained 14-1 chance travelled superbly throughout the two-mile-five-furlong contest and took up the running soon after jumping the second-last.
He showed a smart turn of foot to put distance between himself and his rivals and although Mirage Dore stayed on late up the hill, Ninetieth Minute had a length and a half in hand at the line.
Pause And Clause (9-1) rewarded each-way backers by finishing third, while Star Of Angels (40-1) was fourth.
It was a first ever Festival victory for Flood, who appeared confident that he had plenty of horse under him.
Mirage Dore was under the pump before the turn for home but found plenty for Rose Dobbin, while the well-fancied Pause And Clause appeared in trouble at the top of the hill but kept responding to Jack Doyle.
Last year's County Hurdle runner-up Psycho was well fancied to go one better but flattered to deceive and failed to land a blow.
Taaffe said: "He's owned by Dermot Cox, who was the brainchild behind the development of Punchestown.
"His wish is for us to rough the horse off and bring him back over fences next season - although there is a slim chance that he could run over hurdles at the Punchestown Festival."
Flood said: "You can't describe the feeling, it's just 'wow'.
"People say it's the best feeling ever, but you don't understand until it happens. It's powerful.
"He didn't travel early, he didn't travel great.
"He's a big horse, he has a big stride on him and it took me the first half of the race to get into a rhythm.
"I didn't get a nice position until we got to the top of the hill, but to be fair to him he's as tough as nails.
"All his races he's won this year I've gone on with him early and he gallops on.
"Tom has been super to me this season, he's been great. I can't thank him enough."
Lucinda Russell expressed disappointment at finishing runner-up in the race with Mirage Dore.
"It's an anti-climax to be second," said the trainer.
"He was further back than we'd planned and Rose (Dobbin) did very well to get so close in the end.
"Our plan nearly worked out and he'll probably go to Aintree now."
Emma Lavelle was left dreaming of a bright future for third-placed Pause And Clause.
She said: "It was only his fourth run over hurdles and he put his heart and soul in it today.
"I probably won't run him again this season but I really think he's a very exciting prospect."