I Was A Rat! is Philip Pullman's enchanting story for younger readers about Roger, a scruffy page boy who turns up one evening on the doorstep of old married couple Bob and Joan.
"I was a rat!" he insists! But what is he now? A terrifying monster rampaging in the sewers? A money-spinning fairground freak? A champion wriggler and a downy card? Or just an ordinary boy, though a little ratty in his habits?
Now the story has been brought to life on stage in a co-production between Teatro Kismet from Italy and Birmingham Repertory Theatre.
Taking the leading role is the delightfully named Fox Jackson-Keen – "when I was born my dad loved The X-Files and named me after Fox Mulder, so I was pre-destined to be an actor", he laughs.
Although still a few months short of his 18th birthday, this isn't the first time Fox has played a lead role. When he was just 13, he became the first Londoner to play Billy in Billy Elliot the Musical.
Fox says I Was A Rat! is completely different from Billy Elliot.
"In Billy Elliot, the company really supported me to understand Billy. I was creating my own version of Billy but copying what had been done before. For this I was able to create Roger myself," he says.
"I am working with amazing, talented actors who can all play instruments and do juggling. It's a big jump – it's like me growing up, and Roger growing up."
Fox originally followed in his dad's footsteps. He was a gymnast, the best in London in his heyday, and Fox enjoyed gymnastics too, before widening his interests at theatre school. He was 11 when he first auditioned for Billy Elliot. "They said I was OK in ballet, tap and acrobatics but I was a bit too small and should come back next year. To be honest, I forgot about it! But I went back and got the part.
"Everyone is so thoughtful and looks after you. The older Billys really shaped me as an actor.
"If it wasn't for them, I wouldn't be where I am now. I can almost never be too thankful for that. I suppose there is a bit of the Billy Elliot story in me. You go in an audition and you slowly become the story of Billy Elliot and have all the same feelings he has."
There are similarities between Billy and Roger who is a "pure-hearted boy", says Fox.
"Roger is amazed at everything he sees. The world is seen through his eyes. Things appear grotesque, or they can appear evil, or the complete opposite, really sweet and funny.
"He really wants to fit in, to be part of something. He is torn between being a rat and a boy. It's a very emotional show and it's been adapted so brilliantly. It's a gift to play.
"I used to read the Philip Pullman books and I know his writing," says Fox. "I used to listen to the His Dark Materials tape as a kid. and I used to listen to I Was A Rat!
"It's a fairytale and like all great fairytales, there are bits for kids and bits for adults. There are bits of slapstick in the show which the whole family can enjoy, but the story also touches so many people."
In the theatrical world, Fox is still very much a cub who finds himself away from his London home for the first time. "I've only ever been to Birmingham – for this show – so every single place is new. But this is the right time for me to play this role and I absolutely love everything about this show."
I Was A Rat! is at the Hall for Cornwall, Truro, from April 23-25 and the Northcott Theatre, Exeter, May 15-18.