Sitting in a row in front of me were three highly accomplished, professional actors, awaiting my first question. It was, I must admit, just a little intimidating — almost as if Dames Maggie Smith, Judi Dench, and Helen Mirren were lined up for interview together.

But, no disrespect, these actors are rather younger: Adrianna Bertola, Josie Griffiths, and Kerry Ingram are aged 11, ten, and 11 respectively.

Their CVs are, however, already impressive. Between them they can boast (not that they do boast, they are far too well-mannered) runs in the West End productions of Hairspray, The Sound of Music, Annie and Billy Elliot, while there has also been a nine-month tour in Chitty Chitty Bang Bang, an appearance in the film Robin Hood, and another nine-month stint, this time in BBC hospital drama Casualty.

Now Adrianna, Josie, and Kerry are to alternate the title role in this year’s RSC Christmas show: a brand-new musical adaptation of Roald Dahl’s children’s novel Matilda.

The story, you will doubtless recall from either the book or the 1996 film, is about Matilda Wormwood, an extraordinarily talented child who learns to read at the age of two.

“I thought it was really interesting that she was two years old, reading books, and really good at maths and things like that,” Kerry said in admiring tones. “I start reading at five or six, and only started being bright at maths in year three.”

“I thought it was pretty amazing that she could really read at two, and if someone asked her a question, she’d know the answer straight away,” added Adrianna. “That’s quite cool.”

“I’m the same as Adrianna, I thought it was cool too,” Josie agreed. “But I was never like that myself!”

Adrianna, Josie, and Kerry have landed the role of Matilda after a gruelling series of auditions.

“It wasn’t really nerve-wracking, but there were so many auditions!” Adrianna explained. “They seemed to go on for ever, I think there were about eight of them altogether.

“Then there were workshops, and even then you didn’t know if you had the part.

“I kind of messed things up at my first audition. I sung my song to the wrong tune, and I went back to the green room and burst into tears. Then they called me back several times, it felt like forever. Finally I did a dance with Josie, and at about ten o’clock at night my mum received an email saying I’d got the part.”

Matilda’s extraordinarily nasty parents have no time whatsoever for their daughter's prodigious abilities.

“It’s almost as if he’s got a manifesto: TV is good, books are bad,” said Paul Kaye, who is playing Mr Wormwood. “He can’t work out why anybody would bother spending time flicking through books when it’s all there on TV. If you took that TV away, you’d remove 80 per cent of his personality. He’s confronted by Matilda, who he is convinced is just a weird boy: he can’t even admit he’s got a daughter.”

It’s often said that nasty characters are the most fun to play, and Paul is plainly relishing the chance to play a pig-ignorant man who, in Roald Dahl’s book, purveys exceedingly dodgy second-hand cars.

“He remains a second-hand car salesman, but they’ve changed the story. Now he’s ripping off a group of Russian businessmen: he’s reversed the mileages, and dressed them up as brand-new cars.

“Basically, he knows how to polish a turd. But the businessmen turn out to be Mafia, and he gets in way above his head.”

When I met writer Dennis Kelly, it became clear that he, composer Tim Minchin, and director Matthew Warchus, have cooked up a number of other changes to Dahl’s original book.

“I was in a café, and the waiter asked what I was working on,” Dennis told me. “When I said it was Matilda, he went mad for it, he remembered every detail. You suddenly realise that people aren’t coming to see our version of Matilda, they’re coming to see the story itself. You have to abandon the original, yet respect it. It’s a really difficult balance, but I hope we’ve got it right.”

Matilda, A Musical runs at the Courtyard Theatre, Stratford-upon-Avon, from November 9 to January 30. Tickets from rsc.org.uk or 0844 8001110.