Ruler Of The World provided Aidan O'Brien with a fourth Investec Derby and maintained his unbeaten record under Ryan Moore at Epsom - with favourite Dawn Approach well beaten after racing far too free.

Dawn Approach failed to settle from very early on and Kevin Manning felt he had no option but to take up the running on the approach to Tattenham Corner, with the writing being on the wall some way out.

Ruler Of The World (7-1) showed a smart turn of foot to go clear, but Battle Of Marengo, Galileo Rock and Ocovango all set off in pursuit.

The gap was closing at the line as Libertarian flashed home to claim second with Galileo Rock in third.

In the early stages Joseph O'Brien on Battle Of Marengo set a pedestrian gallop and with Dawn Approach wide with no cover and still pulling, Manning was forced to play his hand early.

Moore had the eventual winner just on the outside of Ocovango as the pace quickened and the French raider had to take a pull, forfeiting valuable ground.

Galileo Rock was handy throughout and stuck to his task gamely, outrunning his big price, but arguably the horse to take from the race was the unheralded runner-up, who was catching the winner with every stride, going down by a length and a half.

Battle Of Marengo was fourth, but Dawn Approach was eased markedly, beating just one home.

Moore said: "I wanted to be a bit closer, but I just didn't get away very well and it was a very messy race.

"I had no option but to go on when I did, I knew he'd stay the trip very well but I got there a bit soon and he was very green.

"He's improved a lot from Chester and he'll get further. He's got a really likeable attitude.

"I knew the others were coming because I'd gone too early, but he really toughed it out and showed a very good attitude."

He added: "I'm very lucky to be in this position and on these horses. This is the most important race for me."

O'Brien said: "We're just so lucky, we get these incredibly-bred horses and even before they are mated the dream is for this to happen.

"The owners understand the game so much, they are given all the information and usually come up with a plan and we try and carry it out.

"All the jockeys had their own plan and all the horses were doing their own thing and that is just the way it ended up.

"This horse was impressive at Chester (winning the Chester Vase) and won like a very good horse.

"It's incredible, we're very privileged to be in the position we are."

Coolmore supremo John Magnier said: "Joseph had his choice (of what to ride from the Ballydoyle runners) and Aidan thought this horse was the next best.

"That's why the Derby is such an interesting race, as it is all unfolding.

"The weather has been so difficult, we haven't really been on the grass much and if you try to find out everything at home you are not going to win the Derby."