While Tom Hanks and Emma Thompson head up the posters and marketing for Saving Mr. Banks with their turns as Walt Disney and P.L Travers; the roles of Jason Schwartzman and B.J. Novak as Richard and Robert Sherman – composers during Disney’s pomp – are just as pertinent and significant to the story of Mary Poppins’ journey from page to screen.

Saving Mr BanksTravers herself wasn't a big fan of made up words

The brothers, who are now separating following Robert’s death, were responsible for the most-loved, iconic music in movie history, including ‘Trust in Me’ from ‘The Jungle Book,’ ‘Chitty Chitty Bang Bang’ from… you guess it; the theme tune for ‘Winnie The Pooh,’ and ‘Bedknobs & Broomsticks’.

It is, however, for their work on ‘Mary Poppins’ for which they are most fondly recalled. The Oscar-winning ‘Chim Chim Cher-ee,’ ‘Supercalifragilisticexpialidocious,’ ‘A Spoonful of Sugar’ and ‘Feed The Birds’ all rank high amongst Disney lovers. “Those two weeks I would hate to go through again,” Sherman, 85, said to HitFix.

Read our review of Saving Mr. Banks

“Mrs. Travers was very, very difficult.” Indeed, Saving Mr. Banks does focus on the tension between Walt Disney and Travers as they tried to secure a deal for Mary Poppins to be reimagined in cinema. “When we first read the books, we thought ‘There’s no story here. We have to tell the story,” explained Sherman.

“There’s a reason Mary Poppins comes. It’s because it’s an unsettled household. The father’s paying no attention and the mother is off with the suffragette movement. This is stuff we trumped up.”

BJ Novak and Jason SchwartzmanB.J Novak and Jason Schwartzman play Robert and Richard Sherman

The Shermans become staff writers at Disney following their plot additions to the now-legendary Poppins lore, under the wing of a father-like Walt Disney. Disney. He “was like a second father. We both loved him,” said Sherman. “Let me tell you something, a lot of people talk about Walt in negative ways. There was nothing negative about Walt Disney,” he says. “He was dedicated to doing great things. He reached for the stars all the time. He was a wonderful, wonderful boss.”

Like the story that led to the film that made Saving Mr. Banks possible, there was trouble in getting the Hanks/Thompson project off the ground. So much so that Disney are planning a documentary-style movie called Saving Mr. Hanks, which documents just how difficult it was to get things moving.

But for Richard Sherman, who played such a big role in making Mary Poppins what it is today – a cherished family favourite the world over, simply working with his brother on the original meant the world to him. “It meant so much to us,” he says. “We knew this would be the doorway to our success as songwriters because we had been writing songs and had a couple of hits, but nothing huge. This was a huge thing for us.”

Watch the trailer for Saving Mr. Banks