The three-time winner of the Premier Classic has opted for the colt whom he partnered to victory in the Derrinstown Stud Derby Trial, rather than go for the 2000 Guineas third.
O’Brien is set to have four runners, with Christophe Soumillon aboard Dante runner-up Seville, Colm O’Donoghue riding Treasure Beach and the trainer’s son, Joseph, on Memphis Tennessee.
The riding arrangements were announced by O’Brien’s wife, Anne-Marie, on her Twitter account.
Meanwhile Johnny Murtagh has emerged a contender to ride Native Khan.
Dunlop had earlier in the day approached Olivier Peslier, who partnered Native Khan into third place in the 2000 Guineas, but the French veteran has been retained by the Wertheimer brothers to ride at Longchamp on the same afternoon.
The Aga Khan retained Murtagh neither confirmed nor denied the speculation when approached at Ballinrobe last night.
He did, however, reveal to be “in the running” to ride in the mile-and-a-half showpiece at the Surrey venue.
“I have to speak to the Aga Khan first and I won’t be saying anything until tomorrow,” said Murtagh, who rode Dunlop’s mighty Ouija Board in the 2004 Arc.
Fallon, also a three-times winner of the Derby, has opted for Recital, whom he partnered to victory in the Derrinstown Stud Derby Trial.
O’Brien has also left in Roderic O’Connor among the 17 horses confirmed at the five-day stage, but the Irish 2000 Guineas winner is instead likely to run in the French Derby at Chantilly on Sunday.
Carlton House is the hot favourite to give Queen Elizabeth a first victory in the Derby.
“Carlton House is on target for Epsom,” said the Queen’s racing manager John Warren.
“He had a nice blow yesterday at Newmarket and the trainer is very happy with him at this point.
“Carlton House will be kept ticking over this week.
“There is excitement all round and I think the whole country is starting to focus on it and everyone is excited by the prospect.”
Godolphin’s hopes appear to rest with Ocean War – though Sheikh Mohammed’s operation have also left in Casamento and Genius Beast as a precaution.
“We are very much leaning towards Ocean War as being our Derby contender, with Casamento going for the Prix du Jockey Club and Genius Beast waiting for the King Edward (at Royal Ascot),” said Godolphin racing manager Simon Crisford.
“All three have stayed in at the confirmation stage, that gives us a little more time as a precautionary measure in case we have to change our plans at the last minute, but as things stand that is what we’ll do.
“Ocean War has done very well – he’s unbeaten this season.
“What we like about him is his very tenacious attitude.
“We’re pretty certain a mile and a half will suit him very well.”
“We think a true-run race will help him and we expect to see him to do all his best work at the finish.
“On the book we know he’s got plenty to find and he’s got to improve a great deal on what’s done so far, but he’s done nothing but please us.”