Emma Thompson has confessed how much she enjoyed being so rude as writer PL Travers in Saving Mr Banks.
The actress plays the cantankerous Mary Poppins author in the film, which is about Walt Disney's battle to persuade her to sign over the rights to her character so he could make the now famous musical adaptation starring Julie Andrews and Dick Van Dyke.
Emma admitted: "It's such a relief to be rude really, without any repercussions whatsoever.
"Can you imagine it - 'I don't want to come out to your f***ing press conference because I'm bored with them.' Or, 'I don't want to come out to your birthday party because I got bored of you years ago!'
"If you could just come out with these things, and she did - she just said it. I know I do that sometimes and get into terrible trouble and probably will now, but that was what was so great."
The film co-stars Tom Hanks as Walt Disney and Colin Farrell as PL Travers' father Travers Goff, and Emma revealed they all got together at Colin's house to watch Mary Poppins before they started filming.
Emma revealed: "The first night we were all together in LA, Col had us over to his gaff and showed the film Mary Poppins and that's the last time I saw it.
"And we all sat there marvelling at it and going 'Oh my God I'd forgotten that bit,' and then, 'Oh my God it's so long!' Because we were there for days, it seemed! But it's an extraordinary piece of filming."
Saving Mr Banks is released in cinemas on November 29 2013.