The man Lyra meets on the train is elderly and immaculate. He has a moustache and heavily lidded eyes. He wears a fez. Over the course of the journey Lyra learns that he speaks perfect French and that he has a mysterious pack of cards that he uses at one point to entertain a child travelling in the same compartment.

There is something special about these cards. They are narrower than ordinary playing cards, and each one contains an image – a road, a group of people, maybe a building – that can be laid next to any other card to fit together “seamlessly”, continuing the picture and bringing all elements into a single shared context. Portraits that come together to form a landscape.

When the man uses the deck to entertain the child, he builds a story with each card. There is a method to it: immaculate. “As he mentioned each event, each little object, the old man touched a silver pencil to the card, precisely showing where it was.” Eventually the cards will belong to Lyra, and they will help her, in some dim and peculiar way, to divine the state of things in the world about her. And they will have a name: Myrioramas.

I found the cards, the old man, the train and the carriage, half-way through Philip Pullman’s recent book The Secret Commonwealth, which I read over Christmas. The Secret Commonwealth is the latest entry in Pullman’s Book of Dust series, a collection of fantasy novels that continue the narrative started with the His Dark Materials trilogy. And as such these books are filled with marvels, from the animal daemons that each human shares their life with, to Lyra’s Alethiometer, a sort of pocket-watch contraption that allows Lyra to find out the truth about things by interpreting symbols. I assumed the Myrioramas were, like the Alethiometer, an invention of Pullman’s. They’re a lovely conceit, superficially mundane and yet quietly magical in their seamless way of slotting together in endless arrangements. And then there’s that name, surely made for the long loops and arcs and bows of art nouveau printing. A strange shop in a forgotten alley, a sign beckoning underground: Myrioramas!