Interview and words by Helen Boyle and published with permission from Bloomsbury UK and Jonathan Ball publishers.

“So I got this phone call from my agent,” illustrator Jim Kay tells me, “and she said, ‘Are you sitting down? They want you to illustrate Harry Potter.’ As a big fan of the books and the films, Kay explains, “It was an incredible opportunity to design Harry’s world from the bottom up.”

But does the commission of a lifetime also come with the pressure of a lifetime?

“Yes, definitely. Everyone has an opinion on Harry Potter and that’s why it’s great, but that’s also why it’s challenging. But I’m not complaining, it’s an amazing commission.”

And Jim Kay likes to challenge himself. “My old art teacher used to say you have to keep testing yourself, don’t get comfortable. And I knew Harry Potter would be difficult for me: because it is children, because of the scale of it and because it’s fantasy. I probably think of myself more as a printmaker, expressing things through landscapes, but with Harry Potter I had to express emotions through characters.

“The hardest thing was the casting – I had to find my own Harry, Ron and Hermione. I’ve never really drawn children, so I needed actual references, especially as the kids grow up through the books. So my agent and I had to find children to cast as my characters.”