I am, of course, a frustrated rock star - I'd much rather be a rock star than a writer. Or own a record shop. Still, it's not a bad life, is it? You just sit at a computer and make stuff up.

At all times, think like a writer, and keep those antennae twitching - that way, you pick up new ideas.

Witches never existed, except in people’s minds. All there was in the olden days was women and some men who believed in herbal cures and in folklore and in the wish to fly. Witches? We’re all witches in one way or another. Witches was the invention of mankind, son. We’re all witches beneath the skin.

I started writing novels while an undergraduate student, in an attempt to make sense of the city of Edinburgh, using a detective as my protagonist. Each book hopefully adds another piece to the jigsaw that is modern Scotland, asking questions about the nation's politics, economy, psyche and history ... and perhaps pointing towards its possible future.

I don't think I have one particular favourite writer. I have many whose works I will always buy or reread - Muriel Spark, Anthony Powell, Robert Louis Stevenson, Ruth Rendell, James Ellroy, William McIlvanney, Kate Atkinson, John Burnside, Louise Welsh, Iain Banks.

My first novel was turned down by half a dozen publishers. And even after having published five or six books, I wasn't making enough money to live on, and was beginning to think I'd have to give up the dream of being a full-time writer.

I'm often asked how I write books, but I don't think my approach is suitable for everyone. If I walked into a creative writing class, all I could say to them was 'I tend to make it up as I go along.' I'm not sure that's brilliant advice.