Terry's written loads of books for adults, including 26 in the massive Discworld series, and just eight novels for children.
"I'm amazed," he said. "I think the children's books field is far more competitive these days, there is such a lot of good stuff out there.
"Writing for children is harder than writing for adults, if you do it properly. What I thought was going to be a funny little story about a cat organising a swindle turned out to be a major project.
"The first novel I ever wrote was a children's book. I have written about eight now. I haven't quite got my foot in the door of the children's book world, but I think I have three toes in.
Happy about Harry