Mr Vander Ark said his Potter involvement had been an important part of his life for the past nine years. He had only wanted to celebrate Ms Rowling's achievement in creating a rich and magical world and had sought to create a reference guide for readers.

Earlier, Mr Vander Ark appeared pleased to learn Ms Rowling had found fault with his analysis of the origins of some of her language. Told that a term he thought was derived from a Hawaiian greeting was in fact from a West African language, he asked "Which dialect? …That's very exciting stuff for someone like me."

• What songs do wizards use to celebrate birthdays?
• What sports do wizards play besides Quidditch?
• What have you learned from the Harry Potter series that you use in everyday life?

The formation of this childrens' list was - of course - a very astute move. It was launched by Barry Cunningham, a Bloomsbury executive who, in 1997, received a manuscript from an old agent friend of his, Christopher Little. The manuscript was from an Edinburgh single mother called Joanne Kathleen Rowling.

Newton says that part of the original manuscript was passed around at the weekly editorial meeting. He also showed it to his then-eight-year-old daughter Alice, who gave it the thumbs-up. Bloomsbury bought the first two books for a reported £2,500. The first Harry Potter had no marketing budget, but was a word of mouth phenomenon. Did Newton ever imagine it would be this big? "Of course not. A publisher can tell if a book is good, and might be able to tell if it will be big, but no-one can predict worldwide sales of 357m across 65 countries," he says.