Domhnall will play the literary bear's creator, A.A. Milne, while Margot will star as his wife Daphne in Goodbye Christopher Robin. Simon Curtis will direct the film about Milne's relationship with his son, Christopher Robin, who inspired the tale about the boy and his cuddly toy bear.

"I am delighted to be collaborating with (screenwriter) Frank Cottrell Boyce to tell the remarkable and poignant story of the family behind the creation of Winnie the Pooh," Curtis says. "We are assembling a wonderful cast, headed by two actors I am longing to work with - Domhnall Gleeson and Margot Robbie."

Goodbye Christopher Robin isn't the only Winnie the Pooh story in development - Disney studio bosses are reportedly developing a live-action film, which will revolve around Christopher Robin's return to the Hundred Acre Wood, where Milne's stories were set, as an adult.