Torchwood and West End star John Barrowman has written his first children’s novel with his journalist sister Carole. As they prepare to sign copies of Hollow Earth in Kent, Chris Price caught up with the pair.

What inspired the idea of twins who could make artwork come to life in Hollow Earth?

JB: After we decided that Matt and Em’s [the twins and main characters in Hollow Earth] amazing imaginations would be their superpowers, having them move in and out of paintings came to us right away in one of our brainstorming sessions.

Is there an underlying message? What do you want kids to take from the book?

CB: We hope children are entertained, that they love the characters and the story enough to want to read more, draw more, paint more or even want to learn a little more about the art and artists in the book.

JB: If one or two children go to an art gallery or ask for a sketch pad after reading Hollow Earth, that would be brilliant.

How do you come up with your ideas?

CB: Oh, we have a million of them… powerful imaginations are our super powers too.

JB: When we finish a project together, we always try to have the next one lined up… so we started generating ideas for Hollow Earth months before we pitched the idea to Buster Books.

Why did you decide to go into children’s fiction, rather than adult?

JB: When we were thinking about doing another project together the ideas we came up with were all for a children’s book. We also still read quite a bit of children’s fiction on our own. Most of all, I think we’re still kids at heart.

What was your favourite book as a child? What is your favourite book now?

JB: We both loved adventure stories and mysteries when we were young. Carole is older and read a lot as a kid so she’d pass her books down to me. I loved comic books and Treasure Island and The Secret Seven. Right now I’m reading books about Peru for another project we’re working on together – a Torchwood novel.

CB: I remember reading and re-reading Dodie Smith’s I Capture the Castle as a young girl. I wanted to be Cassandra. I’m teaching The Hunger Games this term. I’m re-reading Suzanne Collins trilogy right now.

Was there ever any bickering about what should go into the book?

CB: We share similar sensibilities about life and art and don’t take ourselves too seriously. Plus I’d just remind him that I’m his big sister and I’m always right.

JB: I’m the wee brother so I’m never wrong. We have a good laugh when we work together and we respect each other’s talents. It probably doesn’t hurt that we’re not always on the same continent.

Before appearing in Doctor Who, was science fiction always an interest for you, John?

JB: Always. I’m from the light saber generation. I’m a huge Star Wars fan. In fact, my nephew, Turner and I still collect Star Wars figures. I loved the original series of Battlestar Gallactica.

What are your plans for this year?

JB: Lots of exciting new TV projects and a Torchwood novel in the fall with Carole.

John and Carole E Barrowman will sign copies of their children’s novel Hollow Earth at Waterstones in Bluewater on Saturday, February 4 from 1pm. Call 01322 624831. Hollow Earth is published by Buster Books and costs £6.99.