Streep added that Disney "supported an anti-Semitic industry lobbying group".

It's enough to make any Disney executive choke - seeing the founding father of the company brought to task by a Hollywood legend. After all, Walt Disney is not just a name; it's a brand - one that stands for family values and entertainment. And in a year that marks the 50th anniversary of - at the time the most expensive Disney Studios film - it risks sullying the image of one of its most beloved movies.

Even Hanks admits that playing Disney was "a burden", adding "I did not do it lightly", He is, after all, part of the family - voicing Woody from the series, produced by the Disney-owned Pixar. "You see the history of the studio absolutely everywhere," he says.

Yet is not Walt Disney's story. "It's not a Walt biopic. It's two weeks of his life in 1961," states the film's director, John Lee Hancock. Instead, it's really about Travers - here portrayed by Thompson as a prickly eccentric desperate to guard against the sugar-coating of her beloved creation, the stern children's nanny whose adventures were chronicled across eight books. And with good reason: "They're actually quite dark, the books," says Kelly Marcel, ' screenwriter (along with Sue Smith). "They really are. They're very, very different."

Dubbed "two great juggernauts thundering along a railway line, toward each other, doomed to collide" by author Brian Sibley, it's the testy relationship between Travers and Disney that drives the film. Walt Disney, as we learn, chased the rights to for 20 years because he made a promise to his daughter. Forced to sell the rights due to her own precarious financial position, Travers wasn't going down without a fight, protesting against everything from the use of songs to the animated interludes.

"She really didn't like the film," says Marcel. "She went up to Walt Disney at the [post-premiere screening] party afterwards and said, 'Well, it's awful. We're going to have to start all over again.' And he said, 'I'm afraid that ship has sailed Mrs Travers.'" And indeed it had. The film became Disney's biggest hit of the 1960s. It gained 13 Oscar nominations - a record for a film released by the Walt Disney Studios. It won five, including best actress for Julie Andrews' work in the title role.

is about more than just an author facing creative dilemmas, however. As any fan will tell you, "Mr Banks" is the father of the children cared for by Mary Poppins, and Hancock's film attempts to show that Travers had her own daddy issues. She was born and raised in Australia, under the name Helen Goff, and her own father, Travers Goff, struggled with alcoholism and was barely able to keep down his job managing a small town bank. By writing Mr Banks, Travers had hoped to somehow "save" - or at least absolve - her own father through storytelling.

This story element is arguably why the film got made in the first place, for it began life not at Disney Studios but in Australia with Hopscotch Films as a Travers biopic. Later, the BBC got involved, with producer Alison Owen (whose credits include ) furthering the film and bringing Marcel on board. Only then was, as Hancock puts it, the script "tossed over the wall to Disney corporate". The way he sees it, "If this had been developed in house [at Disney], it probably would never have been made or wouldn't be very good."

Of course, due to the copyright issues surrounding the script's liberal use of Disney's movie - everything from the songs to clips from the finished film - no company but Disney could really make it.

Hancock credits the studio with being "brave enough" to pursue it. "I think it's fair to Walt. I think he's [shown as] a human being. I'm not saying there weren't discussions about things, but Tom [Hanks] and I were pretty firm in saying 'This seems right, this seems fair.' And to their credit, they said, 'OK.'"

Still, the film has already been criticised for airbrushing facts - everything from British director Robert Stevenson's contribution to making to Travers' unruly relationship with her son, Camillus. Most noticeably, Disney's chain-smoking habit - one that would lead him to die of lung cancer - has been largely stubbed out. "In a meeting, he would be smoking up a chimney!" concedes Hanks. "But that's very hard to show ... even James Bond doesn't smoke anymore."

It didn't help that back in 2007, Bob Iger, Disney's chairman and CEO, stated, "We expect the depictions of cigarette smoking in future Disney-branded films will be non-existent." Still, Hancock and Hanks argued that along with his penchant for Scotch (and the occasional swear word) it needed to be shown, even if we only briefly see him finishing a cigarette in front of Travers. "I think that's enough," says Hancock. "It's a tip to that without having to show him with an ashtray full of cigarettes all the time."

For Hanks, one of the big problems was uncovering who the real Disney was. "The problem was the vast majority of film on the man is him performing as himself," he says. Frequently seen fronting television shows like , "everything was him performing as the icon that we already knew he was". Access to friends and family, including his 79 year-old daughter Diane Disney Miller, helped, as did the chance to browse the archives at The Walt Disney Family Museum in San Francisco.

However much his performance may differ from the real man, it hasn't stopped the film from being a roaring success - taking US$70 million in the US, twice its production budget. It's also scored Golden Globe, Bafta and Oscar nominations. Disney executives, however, must be praying that if the film collects any prizes, Meryl Streep won't be presenting the award.

opens on January 30