LONDON - You needn’t have seen the 1964 Disney family staple "Mary Poppins" -- though I shudder to think, almost 50 years after its release, of a childhood completed without it -- to be familiar with the practically perfect English nanny’s all-purpose maxim that "a spoonful of sugar makes the medicine go down." It was a line conceived not by P.L. Travers, the famously prickly Australian author of the children’s books behind the film, but by Richard and Robert Sherman, the Disney studio’s in-house songwriters.

Intentionally or otherwise, it was a cannily appropriate bit of invention: in a sense, it neatly sums up the Disney ethos of using whimsy and cheer to make life lessons more palatable to young viewers. (Or older ones, for that matter.) Disney, after all, was the man who changed the definition of “fairytale” in the public imagination from Grimm-dark allegory to one of mandatory happy endings. Travers, for her part, liked the medicine.

"Saving Mr. Banks," John Lee Hancock’s bright, entertaining and -- inevitably -- somewhat selective overview of "Poppins'" conflict-laden journey to the screen, is a film that aims for the inverse of that formula: a small dose of acrid personal history is applied to make its sentimental study of creative collaboration yielding personal catharsis that much easier to swallow. That's not necessarily a knock against it. If the tidy emotional geometry of Kelly Marcel's script occasionally feels Disney-esque, that seems only right for a film explicitly about the pervasiveness of Disney’s optimistic storytelling principles in popular culture -- and more implicitly about the way even those heightened principles can mirror the odd human truth. Sometimes life is sentimental, and some will fight it more than others.

As played by a hilariously clipped, unaccommodating Emma Thompson -- cutting a rigid figure with her poker-like posture and steel-wool hairdo, seemingly sewn from birth into a tweed skirt suit -- Travers fights that fight with unflagging conviction, protecting her creation in order, as the film’s honey-lit flashbacks make increasingly clear, to protect her own memories. Art adapts life, and life adapts art, several times over in "Saving Mr. Banks," and not just for Travers.

The uptight Australian and the ruthlessly twinkly Walt Disney (Tom Hanks, striking the necessary balance of magnetism and Teflon lack of affect) engage in a civil war for artistic custody of "Poppins"; it’s so hard-fought, we learn, because they've both built their own fantasy empires upon a foundation of personal hardship and a whole heap of daddy issues. Naturally, they can't get along because they have so much in common: it's practically a romantic comedy without a hint of sexual want. (Well, it is a Disney movie, after all.)

"I won't have her careening toward her happy ending like a kamikaze," barks Travers to her put-upon agent, as he approaches her for the umpteenth time in 20 years with Disney's request for the screen rights to her international publishing phenomenon. In 1961, she finally acquiesces to meet the mogul -- she's 61, short on both inspiration and finances -- on the further condition that no part of the film be animated. We all know that Disney would break at least one of those commitments: toward the end of the film, Thompson watches the completed "Mary Poppins" for the first time, and her woebegone expression as dancing cartoon penguins fill the frame is a treat.

But did Disney give Poppins herself a happy ending? Arguably not: played to Oscar-winning effect by Julie Andrews, she remains one of Disney's most sinuous, even sinister, heroines, floating unceremoniously off the screen and leaving the Banks family to their healed devices. It's a bittersweet conclusion that came about as a result of Travers' stubborn script demands at the pre-production stage, made while she held her unsigned contract as collateral. The most enjoyable stretches of "Saving Mr. Banks" aren't, in fact, her terse tête-a-têtes with Disney, but the tortured workshop sessions between the author, screenwriter Don DaGradi (Bradley Whitford) and the Shermans -- delightfully played by Jason Schwartzman and B.J. Novak as stooges with a wily streak, as clean-scrubbed and sharply side-parted as a pair of Disney princes.

Guy Lodge is a South African-born critic and sometime screenwriter. In addition to his work at In Contention, he is a freelance contributor to Variety, Time Out, Empire and The Guardian. He lives well beyond his means in London.