Ten confirmations have been taken so far at the five-day stage for the Group One including the Prince of Wales's Stakes winner.
The Sunday Mirror's Gary Nutting compared the four-year-old to its former Ballydoyle stable-mate Dylan Thomas, who won last year's King George.
He said: "Although Dylan Thomas finished ahead of the Duke in their two clashes last year, O'Brien's (Aidan, Ballydoyle trainer) assertion that the younger horse was not at his best - due to repercussions from a bad injury that curtailed his juvenile career - has been borne out by an official improvement this season of 6lb."
Other entrants being lined-up for the race from trainer Aidan O'Brien's in-form Ballydoyle stable include Mount Nelson, Macarthur and Red Rock Canyon.
O'Brien recently bagged his third successive Darley Irish Oaks with Moonstone earlier in the month, his seventh successive Irish classic.
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