Karen Dotrice, played Jane Banks
Uncle Walt, as I called him, was determined that although I was an eight-year-old working on a film, I should still have a magical time. He flew my mother and two sisters to the US to be with me during the nine months of filming. Whenever we had a free weekend, he'd lend us his plane – called Mickey Mouse – and we would go down to his ranch in Santa Barbara. I was a nervous flyer so he had the plane done out like a sweetshop. When the seatbelt sign went off, we could sell candy to our mum.
I was startled, on the first day, when we were taken to the prop department and a plastercast was made of my bum. It turned out to be for the scene where we slide up and down the banister. The cast was made into a seat that fitted under my clothes. When a button was pressed, off we went like we were on a Stannah stairlift.
My dad was working in London and we only saw him once during our time away. So Dick Van Dyke became a father figure to me. He was like a big baby – he would muck about on the sidelines and then, as soon as the camera started rolling, put on a straight face. But I'd be piddling myself laughing and couldn't get myself together, meaning there were many retakes.
It was an emotional time for Julie Andrewsas she was in the middle of a divorce, but she still managed to really send things up with Dick, especially the scenes with the cartoon animals. Because the special effects were filled in later, we had these large, sweaty prop guys in braces dancing about with cut-out horses and penguins to show us what was going on. They both tried hard not to cuss in front of us children.
There were so many retakes of the Supercalifragilistic scene that we got sick of the toffee apples we were supposed to be eating. So the prop guys would let us order whatever flavour we wanted for the next day's shoot. We got through raspberry, chocolate, even cinnamon, and then after two weeks just gave up.
I had learned all the songs before leaving England. My teacher was about 108 and taught me to warble them like in an operetta, so when I first performed in the studio everyone was pissing themselves. Julie took me aside and retaught me and when it was time to record them with an orchestra she gave up her day off to support me. I still remember the first time I saw her smoking on set in full garb. I was shocked – Mary Poppins having a fag!
Richard Sherman, co-composer and songwriterWalt Disney handed my brother Bob and I the book Mary Poppins and asked for our thoughts. At first, we were disappointed: the story had no plot. It teemed with wonderful characters but there was no purpose to them. We knew there had to be a reason for Mary Poppins to arrive and leave, so we came up with the idea of a dysfunctional household that needed to be taught about caring for each other. The song Feed the Birds has nothing to do with ornithology: it's about how it doesn't take much to give love.
We didn't know whether the book's author, PL Travers, was a man or woman, alive or dead. It turned out she was a walking icicle. She didn't like anything we did. She resented the fact that the father had been made into a flawed character who changes during the course of the film. She'd made him the hero, an idyllic man, and wanted that preserved; her own father had been a drunk. Showing her our ideas was like walking out of a hot shower and having cold water thrown all over you. Her opening line was that she didn't see why she should meet us since she didn't want music in the film. In the two weeks we spent with her, she managed to destroy all the dreams, hopes and love we had built up.
Bob and I spent two and a half years writing 34 songs, many for sequences that were never used, since we didn't have a final script to work to – two writers had tried but failed to please Walt. The song Supercalifragilisticexpialidocious came about because Bob and I had been to summer camp when we were young, and had held a contest to find a word longer than antidisestablishmentarianism, the longest word in the dictionary. We came up with all sorts of crazy inventions, and were reminded of this when we wanted the Banks children to bring back a non-tangible souvenir from their fantasy adventures.
As well as Bert, Dick also played the old banker Mr Dawes. When he was in costume, he was unrecognisable. He used to wait till lunch on the lot, when people would be going by on scooters, and start to slowly shuffle across the road ahead of them, making them stop. Once they'd gone by, he'd run right past them and start shuffling out again. But the best moment came when I first heard Julie Andrews singing A Spoonful of Sugar. I was crying because she was articulating the whole essence of the movie – which was about the power of love.
• The 50th anniversary Mary Poppins is out on Blu-ray now. Saving Mr Banks is on general release.
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