Trip for Duke will be 'interesting', says O'Brien

Not even the brilliant Aidan O'Brien can be sure Duke Of Marmalade will stay the extra distance of the King George VI And Queen Elizabeth Stakes at Ascot on Saturday.

The 10-11 favourite with Coral goes into the race on the back of three Group One wins already this season after victories in the Prix Ganay, Tattersalls Gold Cup and an imperious performance in the Prince Of Wales's Stakes.

However, he has yet to race over a mile and a half in 12 career starts .

"I'm happy with him and everything has been good since Ascot," said the Ballydoyle handler.

"There's loads of races for him after this and we always take one race at a time, but this is his first time over a mile and a half and we don't really know what is going to happen when he goes past a mile and a quarter, it's going to be interesting."

The decision to run a doubtful stayer in the mid-season championship rather than the likes of Soldier Of Fortune has taken some by surprise, but O'Brien says it was a simple choice.

He told At The Races: "This horse has won three Group Ones and Soldier Of Fortune had already had two runs - we decided to give him a mid-summer break with an autumn campaign in mind so the decision was easy enough.

"He's very good this horse, his physique, pedigree, mentally, attitude, everything about him. He just wins his races and is very professional."