A shrunken granny and a giant chicken may not seem like your dream roles, but for Ilona Sell and Fay Goodwin, being part of a Roald Dahl production at the Oxford Playhouse is a dream come true.

And to make sure they don’t exhaust themselves, the two primary schoolchildren share both parts in George’s Marvellous Medicine. But how did the auditions go in the first place?

“I think I got the part because I love acting, and I think my audition went well. I'm good at screaming,” Ilona, 8, says, who goes to St John Fisher RC Primary School in Littlemore.

“And my character is the very mean grandma when she shrinks and the chicken who drinks some of the medicine that makes it grow huge which is why it is a giant chicken.”

A giant chicken and a shrinking granny. What’s this play all about? “It’s about a boy called George who gets left with his mean grandma and he makes her his own marvellous medicine and makes her disappear,” Ilona (pictured below with Fay), explains.

That still means there are a lot of lines to learn though, so how do the girls manage it? Fay, 9, of Beckley Primary School says: “By reading through my lines a lot and getting my big brother Joey to read the other parts while I say mine. But I really like Roald Dahl books and George’s Marvellous Medicine is one of my favourites.”

So why do Fay and Ilona think everyone loves Roald Dahl so much? “Because he’s interesting, funny and although the stories are impossible he makes them sound realistic,” Ilona says. Fay then pipes up: “And because he has some really weird words and lots of funny ideas.”

As for opening night on Tuesday, are the girls worried about anything? “No, I love playing the grandma when she’s shrinking and going mad - chasing around and shrieking, which very luckily is the bit that I am playing,” Ilona laughs.

“And I have never got stage fright in my whole life!” Fay adds. “I love this play because I can be really grumpy and run around after lots of people and I can look really messy if I have to.”

* George’s Marvellous Medicine opens at the Oxford Playhouse on Tuesday. Box office on 01865 305305.