Marquand, 25, rides Desert Hero for King Charles and Queen Camilla, who are due to be on Town Moor to see if their horse can become the first Royal winner of Britain’s oldest Classic since Dunfermline, for the late Queen Elizabeth II, in 1977.
“It’s a tough race, it’s a Classic and there are only five a year and there’s a reason why they are so hard to win,” Marquand told The Yorkshire Post.
“He’s an extremely exciting horse and has done everything right so far and it is going to be interesting.”
The jockey had ridden Desert Hero, who was bred by the late Queen, a huge fan and supporter of racing, to victory in three of his four career wins.
The most notable, for the horse trained by Skipton-born William Haggas, was a first Royal Ascot success for the King and Queen in the King George V Stakes in June, followed by Group 3 Gordon Stakes at the Qatar Goodwood Festival.
He steps up to one mile six and a half furlongs for the first time today, but Marquand doesn’t think that will be a problem.
He said: “From everything he’s been doing at home and on the track he seems fine. He’s been hitting the line hard over a mile and a half and shown no signs of stopping. It is a question mark but I think it's one where we should be just fine.
“He proven on both fast and soft ground and it's drying out but it isn’t something I would be concerned about.
“He ticks all the boxes of what you want from a Betfred St Leger horse. He has speed, he stays, he relaxes right and he’s with the right team, so fingers crossed we get a good trip around.”
Marquand rode his first Group 1 winner in the Lockdown St Leger of 2020 – Galileo Chrome – when regular rider Shane Crosse tested positive for Covid.
“It’s a track I have had a lot of luck at. It would be amazing to win a second one. It makes it extra special having the Royal connection and an exciting prospect of what might be.
“It was clear for everyone to see the joy of the King and Queen when he won at Ascot that was great and their passion for racing was there.
“By the sounds of it they are both extremely excited for the weekend too and it's nice to know that love and passion for racing is there.”
Marquand has a full book of rides today, but Iberian for Charlie Hills in opening Group 2 Betfred Champagne Stakes (1.50) and La Yakel in the PJ Towey Construction Handicap (4.10) for the aforementioned Haggas, catch the eye.
“Both have good chances,” he said.
“Iberian won at Goodwood on his second start and should have learned a bit and La Yakel ran well [to finish second] on his seasonal reappearance and things didn’t go to plan in the Shergar Cup, but you could make valid cases for both.”
Marquand is married to fellow group One-winning jockey Hollie Doyle, who won yesterday’s feature Group Two Doncaster Cup – the third leg of the Stayers’ Triple Crown – with an inspired ride on Alan King’s Trueshan (11-4).
The victory gave the horse an entry into the Melbourne Cup and while plans have yet to be confirmed, Marquand, who recently rode his 1,000th British winner, says he and his wife plan to spend a lot of time abroad again this winter.
He said: “Both Hollie and I are going to head to Melbourne for the Melbourne Cup meeting, hopefully.
“We have also applied for Japan and are hoping we will spend a good bit of our winter out there."
Marquand rode progressive sprinter Big Evs (9-4 fav) to victory in the Group 2 Carlsberg Danish Pilsner Flying Childers Stakes and said: “We are both extremely lucky with the way it is going at the moment so you have got to make hay while the sun shines.”
Malton trainer Adrian Keatley’s Legendary Day (12-1) ridden by Mark Winn held on to deny Ian Williams’ One for the Gutter in the Betfred Mallard Handicap.