Preview: Children's books at Jewish Book Week

His favourite number fact is that 12,988,816 is the number of different ways you can put 32 dominoes on a chess board.

“I love the fact somebody worked it out,” he says, “it makes me laugh.”

He has around 50 routines, so you never know what you might learn at his Book Week talk. Perhaps he will introduce you to flexagons, or infinitely big ice-creams.

Poskitt solemnly confesses he is always making infinitely big holes in things — “there are infinitely big holes swamping York at the moment”.

Kjartan Poskitt will be speaking at Jewish Book Week on March 3

• On March 10 at Jewish Book Week, Horrid Henry creator Francesca Simon and composer Gavin Higgins will talk about transforming Simon’s YA novel, The Monstrous Child, for the Royal Opera House. Not especially an opera fan, Simon drew on her experience of writing picture books — “leaving space for something to be told through the illustrations”. 

The “child” is Hel, stroppy teenager and Norse goddess of the underworld. 

“For the opera, I changed some things because the book is a first-person monologue,” she says. “Hel has a modern teenage voice but also a mythical one,” and the challenge was to preserve her distinctive tones. 

The opera opens on February 21. “It has been the most enormous fun,” says Simon. “In a way, I forget that I wrote it — it’s a thrilling process to see things come off the page on to the stage.” 

JBW director Claudia Rubenstein says: “We’re delighted to be hosting two such incredible children’s and YA authors, enabling families to experience the festival together”. 

Tickets for both talks can be obtained at kingsplace.co.uk/jbw or call 020 7520 1490. Angela Kiverstein is the JC’s children’s books editor