The 21-year-old, who only rode his first winner three years ago and was joint champion apprentice in 2008, replaces Jimmy Fortune. "It's a dream come true to ride for Mr Gosden. He has some great horses and I can't wait to get started," said Buick from Dubai, where he is spending the winter. "While I feel bad for Jimmy, it is the opportunity of a lifetime and it is up to me to take that opportunity and make the most of it."
He added: "I hope to continue to ride for Andrew Balding when I can. The whole Balding family have been great to me over the years and I wouldn't be where I am now if it wasn't for their support and encouragement."
Buick, whose father Willie was a champion jockey in Scandinavia, has spent his career to date with Balding at Kingsclere, and the trainer revealed his mixed feelings at the news.
"Obviously we are very sad to lose him. He's been a valuable asset to the yard, but I think there's no mistaking it's a good career move for him and we wish him well," said Balding. "He's come a long way in a short time and you don't do that unless you've got a lot of natural talent, which he has.
"He's by no means the finished article, but there's better yet to come."
Buick's first winner came at Salisbury in September 2006 and an early big-race triumph came in the Wokingham Stakes at Royal Ascot in June 2007 on Dark Missile for Balding. He landed his first Group 1 victory on the Mick Channon-trained Lahaleeb in the EP Taylor Stakes at Woodbine in October.
Bookmakers believe the appointment makes Buick a leading contender for the 2010 jockeys' championship. William Hill go only 10-1, having taken a 200 bet in October 2006 from one Wiltshire punter to become champion before 2016 at odds of 66-1.