Studiocanal had no comment.
David Heyman, who shepherded the blockbuster "Harry Potter" franchise for Warner Bros., is producing through his Heyday Films banner along with Jeffrey Clifford.
Paul King ("The Mighty Boosh") is directing from a script by Hamish McColl ("Mr. Bean's Holiday") that King also had a hand in shaping. Production is scheduled to start this fall.
Michael Bond's beloved "Paddington" books have sold more than 35 million copies in 40 languages. The first book in the bestselling children's series was published in 1958, though the "Paddington" movie will be a modern adaptation that combines live-action with CGI, similar to box office hits "The Smurfs" and "Yogi Bear."
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Story finds the titular talking bear traveling from darkest Peru to London's Paddington Station where he's taken in by an English family that must protect him from the villainous director of the Museum of Natural History, who happens to be a cold-hearted taxidermist.
Bonneville is making a deal to play Henry Brown, the well-intentioned if somewhat uptight patriarch of Paddington's new family.
The filmmakers would like "House" star Hugh Laurie to voice the role of Paddington but he is not in negotiations at this time, according to individuals familiar with the project.
In addition to handling international sales, Studiocanal is financing and distributing via its subsidiaries in the UK, France and Germany. In recent years, Studiocanal has made a priority of setting up British family comedies with strong universal appeal.
"Paddington," which was originally set up at Warner Bros. in 2007, has been a passion project for Heyman, who has previously been quoted as appreciating the character's optimism, perfect manners and knack for comic chaos.
Heyday, which has Alfonso Cuaron's sci-fi epic "Gravity" opening October 4, recently set Nikolaj Arcel ("A Royal Affair") to direct an adaptation of DC/Vertigo's long-running comic book series "Fables."
Bonneville, who plays Robert Crawley on "Downton Abbey," will soon be seen in George Clooney's period film "The Monuments Men," which Sony will release in the heart of awards season on Dec. 18. His past credits include Richard Eyre's "Iris" with Kate Winslet.
Bonneville is repped by UTA and London-based Gordon and French.