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.