Susan Hill: The Woman in Black author talks evil urges, prison reform and angry drivers

Hill says: 'Dreadful and appalling though the jihadist beheadings are, they have a reason, however twisted it might seem' (Andrew Fox)

Murder is a boring subject There are only certain ways people can kill and it's not very interesting to write about. With my crime novels, I'm not interested in whodunit, but whydunit: most murders are committed within the family, or from within the neighbourhood; very rarely are the police left baffled.

I believe in evil Dreadful and appalling though the jihadist beheadings are, they have a reason, however twisted it might seem. But some people do bad things because they enjoy it; they're psychopaths, people who have no empathy. Which is what my book I'm the King of the Castle deals with [Hill received the Somerset Maugham Award, in 1971, for the book] – this young boy, Hooper, who cannot feel guilt and enjoys making people afraid.

It's hard to write a ghost story about a sunny day Though they don't always have to be set in fog, weather is incredibly important in ghost stories. As is suspense: you've got to turn the screw very, very slowly. When I wrote The Woman in Black [in 1983], I wanted to see whether there was still an appetite for a full-length ghost story, as apart from Victorian titles, there were mostly just lots of short stories out there. It's lovely to see that since I wrote it, there's been a big revival.

When I've finished a book, it goes out into the world to seek its fortune I don't understand it when people get cross about how one of their works was adapted and say, "Oh, they ruined it!" Well, the book is still there. And I love it when others turn my work upside-down and change it; I loved relinquishing control of The Woman in Black [which was adapted into a long-running West End production as well as for film].

Daniel Radcliffe is a fine young actor I was thrilled when he was chosen for the film adaptation of The Woman in Black, because it caused a lot of excitement and I knew he could do it. Though if I hadn't seen him in Equus [in 2007] I might have thought, "Ugh, not little brown specs from Harry Potter." He told me that in between filming the Harry Potter franchise he went back to school, where he was ribbed a lot. He said he got a lot of, "All right, Radcliffe, you're not on set now, so sit down." And I think that helped ensure he was unspoilt.

It's important to give purpose and meaning to prison inmates I'm a patron of the Prisoners' Education Trust and I've met people who've turned their lives around. One young man, a lifer, started taking courses and has just got a PhD from the Open University. Without turning prison life into something more meaningful, prisoners are more likely to reoffend.

We're a nation of patient queuers but angry drivers Get in a car and everybody's tooting and yelling at one another and I want to say, "Your blood pressure's going up; don't worry about it!" The other day I stalled my car at a set of temporary road-work lights, just as it had gone green. We missed the light and everyone was groaning and tooting, and I thought, have you never done that yourself?

My whistling drives people mad I was taught to whistle as a little girl by an undertaker. I used to sit in his workshop, watching him planing wood for the coffins, and he used to whistle all the time – and eventually I started whistling, too. I can whistle anything, particularly trumpet tunes from Classic FM.

Susan Hill, 72, is an author of literary fiction, crime and ghost stories, best known for her novel 'The Woman in Black'. Her new Simon Serrailler crime novel, 'The Soul of Discretion' (£18.99, Chatto & Windus), is published on 2 October. Her new ghost story, 'Printer's Devil Court' (£7.50, Profile), is published next month