I feel myself still like a student learning many things doing films.

I think that it is necessary to implant in children the love for science from the very beginning, and mostly the love for asking questions about the universe, for example why does the sun rise in the morning? Or what allows life on earth? Why earth is so unique compared to the moon? Or about our own body and evolution: what happened to us?

To me, part of what I love about puzzles is that they fuel my curiosity and I’d say curiosity and gratitude are my two favorite virtues. My last book was about gratitude; this book is all about curiosity. Curiosity is what drives puzzlers. They’re like, ‘Why is it? What is it?’

Ultimately, it’s a man who was teaching us English Literature in what we call matricula, the last 2 years of high school. He really was quite extraordinary. When he spoke of a Shakespearean play, you almost thought that he grew up with Shakespeare! He was very good, yes. A black guy who was fantastic and gave us a deep love for literature.

In my early twenties I wrote quite a lot of a very bad novel called The Private Joke. I regularly abandoned it for months at a time to write other things, then picked it up again. Part of the manuscript was sitting up in the luggage rack when, aged 25, I was travelling by train from Manchester to London, and the idea for a very different kind of book hit me: that of a boy who didn’t realise he was a wizard, and was taken off to magic school.

I can remember feeling elated after writing the first Quidditch match, which flowed out of the pen and was barely revised afterwards.

Always… as soon as I knew what writers were, I wanted to be one. I’ve got the perfect temperament for a writer; perfectly happy alone in a room, making things up.

I try to start work before 9am. My writing room is probably my favourite place in the world. It’s in the garden, about a minute’s walk from the house.

So why do I talk about the benefits of failure? Simply because failure meant a stripping away of the inessential. I stopped pretending to myself that I was anything other than what I was, and began to direct all my energy into finishing the only work that mattered to me. Had I really succeeded at anything else, I might never have found the determination to succeed in the one arena I believed I truly belonged. I was set free, because my greatest fear had been realised, and I was still alive, and I still had a daughter whom I adored, and I had an old typewriter and a big idea. And so rock bottom became the solid foundation on which I rebuilt my life.

The friends with whom I sat on graduation day have been my friends for life. They are my children’s godparents, the people to whom I’ve been able to turn in times of trouble, people who have been kind enough not to sue me when I took their names for Death Eaters.