Johnny Murtagh's mount was sent off the 11-8 favourite to add to his wins of 2006 and 2007 in the Royal Ascot highlight, and having been settled in mid-division he swung for home matching strides with market rival Coastal Path, just ahead of last year's runner-up Geordieland.

French raider Coastal Path was the first to break, leaving Yeats and Geordieland to fight out an enthralling finish to the two-and-a-half-mile marathon.

The pair raced upsides throughout the final two furlongs, but when push came to shove Yeats's brilliance shone through and he quickened away to a five-length success.

Aidan O'Brien, winning his fourth Group One of the week, was stunned after his entire became just the second horse to capture three Gold Cups, emulating Sagaro's achievements between 1975 and 1977.

He said: "I can't put into words what this means.

"The lads at home did a great job to get him here for one Gold Cup and then he came back for a second one and now a third one – it's unbelievable.

"I can't see any horse staying with him on the bridle and staring him in the face. It's unbelievable and I didn't really think it would happen.

"He's a great mover with massive lungs and a massive heart.

"You ask most horses to go a mile-and-a-half and that is the limit, but with this fellow his heart is only getting up to 180 beats at that stage. But he is not just a staying horse, he had the class to win a Coronation Cup.

"This is very special for everybody involved. I am very privileged to have these special horses to train."

O'Brien was not without worry in the build-up, with the one-time Derby favourite not having raced since April.

He added: "We decided last year that he would only have the one run beforehand and in the last three weeks I have been sure I have made the wrong decision.

"He has been putting on weight and only doing enough, but the lads have been happy so we have to give them credit."

William Hill make Yeats a 3-1 chance for a record-breaking fourth success in 2009, but his future has yet to be decided.

"I don't know when the time will come to preserve his genes and that is the reality as we've never had a horse with as big a pair of lungs and as big a heart as he has – they are physical things," said O'Brien.

"There is a chance he could go back to Australia for the Melbourne Cup this year. We'll have to discuss the options."

Murtagh was having his first taste of Yeats on the track, but displayed his usual coolness in the saddle.

The jockey said: "He stays the trip well, he has the heart of a lion and I knew that. I knew that if we got there at the four-marker it would take something special to beat him.

"He's got that extra bit of class to come back here and win a third Gold Cup. He doesn't ride like a seven-year-old. I'm just delighted to be part of the team."