The aptly named Ruler Of The World has given trainer Aidan O'Brien his fourth win in the prestigious Epsom Derby and brought up the 10th for owners Coolmore Stud.

While the winners celebrated, connections of the raging favourite Dawn Approach were licking their wounds after he failed to run out the 2400 metres and finished second last.

Ruler Of The World (7-1) came home under Ryan Moore to hold off the fast finishing 14-1 chance Libertarian by 1-1/2 lengths while Galileo Rock (25-1) was third, a further head behind.

"He will not run over 1-1/2 miles again," a shattered Jim Bolger said of Dawn Approach.

Moore, who also won the Derby in 2010 with Workforce, said he thought his horse had hit the front too early when he passed stablemate Battle of Marengo.

"He's very green but he's got plenty of heart and showed it in what was a messy race," Moore said.

"He quickened well and managed to see out the trip. It is a very special day and I am absolutely delighted."

John Magnier, the brains behind the Coolmore breeding operation that feeds O'Brien most of his horses, said there was a measure of luck in their extraordinary success rate in the race named the "Blue Riband of the Turf" by 19th century British Prime Minister Benjamin Disraeli.

"Well there's a measure of luck in this and we are going through a lucky patch," he said.

Before Aidan O'Brien's four Derby winners, the Ballydoyle Stables had sent out six trained by Magnier's late father-in-law, the legendary Vincent O'Brien (no relation).

Asked how highly he rated Aidan O'Brien, Magnier was typically diplomatic.

"Well everyone knows where my father-in-law is rated on the greatest ever list, and Aidan, well, he isn't too bad either, is he!," Magnier said.

"David Wachman (son-in-law of Magnier and who trained the third-placed Galileo Rock) is pretty useful too."

For the connections of Libertarian it was a memorable day as Elaine Burke came the closest ever to becoming the first woman trainer to win the Derby on what was the centenary of suffragette Emily Davison death from injuries sustained when she threw herself in front of King George V's runner in the Derby.

Burke, who trains in the North of England, has been in charge of a 65-horse stable since her husband Karl was disqualified from racing for a year in 2009 for providing information on a horse to a disgraced former owner.

"We can't be anything but delighted," Karl Burke said, suggesting they might pay a supplementary entry fee for the Irish Derby on June 29.