Mary Poppins Returns has gone back to the books written by P.L. Travers for inspiration. The movie, set to be released in December, brings the titular nanny to life once more, this time played by Emily Blunt. Set 25 years after the original Mary Poppins movie, Ben Whishaw and Emily Mortimer play the now adult Michael and Jane Banks. Their former nanny pays a visit when Michael and his three young children are coming to terms with a family death. Lin Manuel Miranda stars opposite Blunt as Jack, a lamplighter who, like chimney sweep Bert before him, knows how magical Mary Poppins can be.

Mary Poppins Returns is a musical and, like Mary Poppins, contains a lively, bright mixture of live action and animation. Its source material, though, comes not from the House of Mouse but from P.L. Travers, who created the nanny as the star of a series of novels. If you've seen the movie Saving Mr. Banks, then you'll know that Travers was exceptionally protective of her character, and was reluctant to let Disney have the rights to her. However, she relented eventually and the movie Mary Poppins was a huge smash. Even now, 54 years after its release, Mary Poppins is a staple movie of many kids' childhoods.

Related: Emily Blunt Didn’t Know About Mary Poppins Books Before The Sequel

Travers actually wrote eight original books about Mary Poppins, and Disney only drew inspiration for the original movie from one of them. So, Mary Poppins Returns has gone back to the books - literally. When we visited the Mary Poppins Returns set, producer Marc Platt explained how the source material tied in perfectly to the era in which the sequel is set:

We went right to the source, we went to P.L. Travers. And it turns out that P.L. Travers wrote eight books, and the original film really capitalizes on only one of the books. And what we found in her books was really a treasure trove of new characters and episodes. And we realized that we could bring the sequel, our own version and our own story, a original story of Mary Poppins all these years later in a very exciting way, but that we could draw upon the original source which is P.L. Travers.

She wrote her books in 1934, 1935. Our film, Mary Poppins Returns, is set in those years, which is the depression era in England. So, it takes place about 25 years after the original film took place.

Mary Poppins Returns Animated Sequence Emily Blunt and Lin-Manuel Miranda

With eight books to choose from, it might have been difficult deciding which one to use as the basis of the story, but Platt took a different approach:

You know, we took from a number of them, actually. Because the books are in some ways a collection of episodes and adventures, and so we plucked some from various books and drew upon a number of them actually.

The trailer for Mary Poppins Returns is full of Disney magic, but it also hints at some sad times to come, something that Travers' novels never shied away from. They were also quite dark at times. If you've ever seen the stage show of Mary Poppins, which included extra scenes from the books, you'll know that to be the case. No doubt Disney have found the perfect mix and will deliver a movie that's practically as perfect as Mary Poppins herself.

Next: Why Rob Marshall Was The Right Person To Make Mary Poppins 2

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