He said: "Neil Callan will no longer ride as first jockey for me this year. However, he will continue to ride for the stable if and when he is available on a freelance basis.
"I would like to thank Neil for his dedication and hard work over the last two seasons. I have enjoyed working with him and we have had a nubmer of good days, most notably his win aboard Eton Forever in last year's Buckingham Palace Stakes at Royal Ascot - my first winner at the Royal Meeting.
"As a trainer I would like a little more flexibility when it comes to jockey bookings. It might be that a 'best available' policy is followed at times. Andrea Atzeni will continue to be given opportunities but also on a freelance basis. There will also be rides for Dominic Fox as there was last season when he returns from injury."