The Ed Walker-trained son of Camelot stamped himself as a leading contender for the premier Classic with a hugely impressive display in the Lingfield Derby Trial earlier in the month and is now a best-priced 7-2 chance, ahead of Andrew Balding’s 2000 Guineas hero Kameko at 5-1.
Marquand was on board English King at Lingfield, but is to be replaced at Epsom by Dettori, who steered the remarkable Stradivarius to a third Gold Cup success at Royal Ascot last week for English King’s owner, Bjorn Nielsen.
"Bjorn has a great relationship with Frankie and the horse is going in with as good a shout as you could possibly imagine. All you can do is respect the decisions of owners," said Marquand on Monday evening.
“He has been pumping an awful lot of money into racing for many years trying to find a Derby winner and he wants Frankie – who he has joined up with for many successes – on board and I respect that.
"Obviously it's kind of trying to get yourself over a bad situation, but it was handled very well by Ed and Bjorn. It was something they spoke to me about before this all came out. The Derby is the Derby, it's something that someone like Bjorn Nielsen has spent the last 30-40 years dreaming of and investing in.
"I want to be a Derby-winning jockey, everyone does. I've just got to respect the decision that they've made. They've got Frankie aboard now and obviously they've got a really strong relationship. Hopefully in the future it's something that can come along again and hopefully the opportunity won't miss me.
"In all honesty no, I wasn't surprised. I was kind of hoping John Gosden would come out with a good horse in the last few weeks! It was always a possibility.
"I suppose being a sportsman you've got to have that bit of self-belief because otherwise you'd never grow and be able to do the job you think you're capable of doing. I'm 22 years of age; hopefully this is something that will happen in reverse in many years to come and I can come across another Derby horse in the future."
The news had first broken on Monday morning when Walker had said: “I feel desperately sorry for Tom, and it is absolutely no reflection of our faith and trust in his ability.
“Bjorn and I mulled it over and watched all the trials, and it became increasingly clear John (Gosden) wasn’t going to have a Derby runner. After Tom won on the horse at Lingfield he asked if he’d keep the ride in the Derby, and I said to him ‘Your only danger is Frankie’.
“Frankie obviously has a wealth of big-race experience and raises his game to stratospheric heights for the big races. We feel very privileged to have him on board.”
Stradivarius was one of six Royal Ascot winners for the popular Italian, who will be bidding for a third win in the Investec Derby following his previous triumphs aboard Authorized in 2007 and Golden Horn in 2015.
Walker added: "The Derby is the Derby, and Frankie is Frankie. It's very tough on Tom - but he has never ridden in a Classic around Epsom before, and I hope he'll have other big days with us in the future, very possibly on this horse.
"It will be my first runner in the Derby - fingers crossed we get there - and having Frankie Dettori on board will just give me a bit of confidence as well, and obviously Frankie and Bjorn have the connection through Stradivarius.
"It wasn't an easy decision. I'm sure it won't be too long before Tom is jocking people off left, right and centre."
English King enjoyed a Monday morning workout in Lambourn and is reported to be in fine fettle by his trainer.
"He's in cracking form - really well in himself. I just hope we can keep him in the same form for the next 12 days," said Walker.
"We haven't organised when it will happen yet, but Frankie will come and sit on him between now and the Derby."
David Stevens represents Coral, who make English King their 7-2 favourite.
"Having enjoyed great success in owner Bjorn Nielsen's silks over the years, most recently on Stradivarius, and with his principal backer John Gosden not having an obvious Derby horse this season, it's not a surprise to see Frankie Dettori booked to ride English King at Epsom next month," he said.
"With no standout Derby challenger from Ballydoyle in the frame yet either, and the Guineas winner Kameko not certain to stay a mile and a half, Frankie's presence on board the impressive Lingfield winner should cement English King's position as big race favourite," added Stevens.
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