IF ONLY she’d stuck to her guns, novelist P L Travers could have prevented Julie Andrews winning an Oscar and spared us the sound of Dick Van Dyke’s demented cockney accent. But no, she said yes to film-making legend Walt Disney and gave him the rights to film her series of books about Mary Poppins.

She didn’t give in easily as this funny, sad film – made under the Disney banner – demonstrates with Tom Hanks as dear old Walt and Emma Thompson as the sharptongued Travers wrestle over the rights to the story of the magical nanny.

We join the story 20 years in – the number of years Travers has resisted Disney’s advances to let him film Mary Poppins. He wants to keep his word to his children who loved the books and to whom he promised to make the heroine fly off the pages on to the cinema screen.

It’s the 1960s and at long last he’s managed to persuade the stubbornly British Travers to fly to Hollywood to resolve the matter once and for all. Some hope as Travers is adamant she doesn’t want her story Disney-fied with sugary sentiment and, horror of horrors, cartoon characters.

Much fun is had at the culture clash as Disney tries everything in his power, including the star prize of taking her on a trip round Disneyland, to change her mind.

When the Sherman brothers sing her songs they’ve written for the film she’s appalled by their use of English. Goodness, she points out, one lyric contains a made-up word. They quickly hide the song sheet headed Supercalifragilisticexpealodocious from her sight.

These meetings with screenwriter Don DaGradi (Bradley Whitford) and the Shermans (Jason Schwartzman and B J Novak) are gloriously amusing as British reserve bumps into Hollywood brashness.

Travers’ unkind put-downs and dismissive attitude may sound like the writers of Saving Mr Banks are making it up, but archive tapes of the meetings played over the end credits show that the makers of this film have actually toned down her behaviour and comments for this movie.

Of course, we know the ending – Mary Poppins was filmed (complete with animated scenes and a big spoonful of sugar) and became a smash hit. But the emotional punch amid all the jollity is provided by the gradual revealing in flashbacks to her Australian childhood of the reasons for Travers’ reluctance to hand over Mary Poppins. Cue flashbacks with Colin Farrell as her drunken bank employee father, Ruth Wilson as her long-suffering mother and Rachel Griffiths as Aunt Ellie, a key figure in the creation of Mary Poppins.

Director John Lee Hancock takes Kelly Marcel and Sue Smith’s script and turns it into an assured, amusing and entertaining exposé with strong performances from Thompson (who played another literary child-minder, Nanny McPhee, on screen) and Hanks.