Aidan O'Brien and Johnny Murtagh were already the major players at this year's meeting and took their third Group One of the week as the even-money favourite poured it on down the straight to collect by four lengths. The mile-and-a-quarter event had hitherto eluded the Ballydoyle team, with even subsequent Arc winner Dylan Thomas having his scalp claimed by Manduro 12 months ago.

But the stage this time belonged firmly to the Tipperary outfit, with Murtagh tracking the early pace before starting to pick off the front-runners two furlongs out.

The Prix Ganay and Tattersalls Gold Cup winner devoured the ground to lead over a furlong out and readily put daylight between himself and his rivals to become the first Irish-trained winner since Stanerra in 1983.

Phoenix Tower, attempting to become Henry Cecil's sixth winner of the race, came in second with Cambridge victor Pipedreamer a short head away in third.

Duke Of Marmalade's three Group One wins this term are in stark contrast to 2007 when he failed to win but made in the frame in several top-class events, including when beaten a neck here in the St James's Palace Stakes.

"He got a fracture in a leg after running at Goodwood as a two-year-old. We had to pin his leg and it was touch and go if we would get him back," O'Brien explained. "He was semi-lame all the time and we had to train him cautiously last year. He was carrying more puppy fat than you would want and was never really 100 per cent.

"Our vet John Halley tweaked the pin and it has made a big difference. He has been much sounder and easier to get fit and has been quickening better in his work.

"He has a lot of options open to him and he's travelling and quickening very well this year.

"We'll have to sit down and talk about where to go, and everything will depend on where Henrythenavigator goes next.

"This fellow could stay at a mile and a quarter and go to the Eclipse, drop back to a mile for the Sussex or go up to a mile and a half for the King George."

Murtagh said: "He was the first horse that I rode when I came back from Dubai (to take the job as retained rider at Coolmore) and we cantered up at the Curragh. He's up there with the best horses I've ever ridden.

"Aidan has trained him for this race all year. He has brought him along slowly and today was the big target.

"He's been showing speed at home and I ride him in a lot of his work. As Aidan says, if we had five or six like him we'd be very happy."

Cecil was pleased with the effort of Phoenix Tower, but was quick to salute the winner.

He said: "He ran really well and is still improving. He is in the Eclipse and the Juddmonte International at York, but I think I underestimated Duke Of Marmalade. I didn't realise quite how good he was."