The Moulton Paddocks handler appeared to hold the ace hand in his bid for a first victory in the Rowley Mile Classic, with last season’s champion juvenile Native Trail the 5-4 favourite to keep his unbeaten record intact and Coroebus also prominent in the market at 5-1.
Native Trail proved his well-being with a comprehensive victory in the Craven Stakes two and a half weeks ago weeks ago, while Coroebus was making his first competitive appearance since winning the Autumn Stakes over the course and distance in early October.
With the pair drawn on opposite sides of the track, they raced wide apart for much of the straight-mile contest, with William Buick the first to get vigorous aboard Native Trail nearest the stands side.
James Doyle, on the other hand, was able to wait until the furlong marker to pop Coroebus the question and he found plenty racing out of the dip to prevail by three-quarters of a length.
Having been under a ride from an early stage, Aidan O’Brien’s Derby favourite Luxembourg made eyecatching late gains to finish best of the rest in third. Paddy Power responded by cutting him to 5-2 for the Cazoo Derby.
Appleby said: "I feel like I felt in the lead up to the race all the way, to be honest - both those horses at every step took a step forward.
"Native Trail came here and won the Craven and the same morning Coroebus came for a gallop and William said he felt very exciting, but he couldn't get off Native Trail with what he'd achieved.
"Coming into today I felt we had two live contenders. The draw didn't worry me. They were good horses racing over a straight line, just keep it simple.
"Like any good horse he has a lot of natural pace and when they have that aligned with the physique you can't help but get excited about them."
He added: "We'll split them up now. It's a nice discussion, but the winner I expect will go to the St James's Palace and Native Trail will go back to the Curragh where he's already won before, he'll go for the Irish Guineas."
Doyle had come close in the Guineas before, notably when beaten just half a length on the brilliant Kingman in 2014.
"He travelled incredibly strongly throughout, there's no reason to believe he won't improve from today because he was exuberant through the early part of the race, I just had to bring him back a couple of times," said the proud rider.
"I was thinking at halfway 'this is all going pretty well', I just thought I'd keep very patient - something joined me quite quick and I just asked him a couple of questions going into the dip and he responded incredibly. If I'd sat a bit longer he'd have been much more impressive.
"This race has been something that has always annoyed me, looking at replays over and over again of Kingman's Guineas and Barney Roy's Guineas, and then it goes as simple as it did today."