Brian Boru was last with half a mile to go

The 5-4 favourite, trained in Ireland by Aidan O'Brien, went head-to-head with High Accolade (8-1) in the closing stages and got the upper hand to win by a length-and-a-quarter .

Phoenix Reach was a further length and a half back in third, with Maharib fourth.

Brian Boru was last half a mile out, but Spencer always had the race under control.

Switched to the outside, Brian Boru quickened in the final quarter-mile and showed tremendous courage to foil Martin Dwyer on High Accolade and become the sixth Irish-trained winner of the world's oldest Classic.

An emotional Spencer devoted the victory to his friend Kieran Kelly, the Irish jump jockey who died last month following a fall at Kilbeggan.

"My good friend Kieran died a month ago - it's all for you, Kieran," said Spencer.

"I said to Pat Eddery after two furlongs that we were going quick and he replied: 'Too fast son, too fast'.

Day four round-up

"So I kept waiitng and waiting. I knew he had a kick and he's done it for me.

"He's very tough and a credit to Aidan O'Brien and his staff."

But there was disappointment for former champion jockey Pat Eddery, who was having his last ride in an English classic before retiring at the end of the season.

He finished unplaced on Westmoreland Road.

Gold Medallist and Summitville cut out the early running with Brian Boru, Moments Of Joy and Westmoreland Road in the rear.

The field bunched up turning into the straight with over four furlongs to run and a host of horses were in with a chance.

But Brian Boru showed class, speed and stamina to win his second Group One at Doncaster following his success in the Racing Post Trophy last October.