Azamour came from last to first to take a thrilling Baileys Irish Champion Stakes at Leopardstown this afternoon.
Michael Kinane timed his run to perfection on the John Oxx-trained colt to deny Norse Dancer.
The 8-1 shot sat at the back all the way round, but Kinane produced him with a blistering late flourish for a half-length win, with Powerscourt in third.
Godolphin's Doyen, sent off the 4-5 favourite, looked set to pounce turning for home but he folded tamely to finish nearly last.
Millstreet, running as pacemaker for Doyen, took them along at a good clip while his stablemate sat on the outside under Frankie Dettori.
Turning for home, Doyen looked the one to be on as he was travelling easily, but when Dettori asked for an effort he found nothing, leaving Powerscourt in front.
John Egan was winding up Norse Dancer for his run in behind and he switched to the outside in the final furlong to get his head in front.
However, Azamour hit top stride and came flying down the outside to just get up in the shadow of the post.
"Mick was obviously concerned that there would be quite a few horses trying to sit just behind the pace and pushing up behind the pacemaker, and he had no option but to hang back," said Oxx.
"He's a very good horse, the fastest in the race, and he was able to use his turn of foot. He pricked his ears a bit when he saw the photographers near the line, but he does that and he ran on well enough, I thought.
"He obviously gets the mile and a quarter well and we have to see whether he gets any further."
Godolphin trainer Saeed Bin Suroor was at a loss to explain Doyen's poor showing.
He said: "I am very disappointed. We will have to see how he comes out of this. Frankie said he was travelling so well but when he asked him to quicken he couldn't."
Doyen had been the 11-10 favourite with William Hill for next month's Prix de l'Arc de Triomphe at Longchamp, but they have pushed him out to 5-2.
Powerscourt has been trimmed to 10-1 from 16-1 for the French showpiece.
Across the water, Rule Of Law put up a brave front-running performance to claim the betfair.com St Leger at Doncaster.
The Godolphin colt took up the running after about three furlongs and was never headed thereafter, despite a strong late challenge from Quiff.
The 3-1 joint favourite, ridden by Australian jockey Kerrin McEvoy, held on by a head from the other favourite, Quiff, while Tycoon was a length and half away in third