I never read any Narnia books as a child, but my two younger brothers were devotees. They insisted upon regaling any audience with the story of how Peter, Susan, Edmund and Lucy pass through into another world.

In the first book, The Lion, the Witch and the Wardrobe (1950), the eponymous wardrobe is the portal. In the fourth, Prince Caspian - which is third in terms of the chronology of the stories, because Lewis wrote a “prequel” in The Magician's Nephew - the children find themselves transported from a country railway station back to the realm of Narnia.

What befalls them there, how they meet Prince Caspian and are reunited with Aslan, I will not say. You might want to go and see the film (above) which opens on Thursday, but there are pleasures aplenty in the book.

For children, Lewis has a simple, direct way of speaking, which is never condescending. Witness this exchange between young Caspian and his wicked uncle Miraz: “‘I wish ... I could have lived in the Old Days' ... Up till now King Miraz had been talking in the tiresome way that some grown-ups have, which makes it clear that they are not really interested in what you are saying, but now he suddenly gave Caspian a very sharp look. ‘Eh? What's that? ... What old days do you mean?'”

And for adults, there are little jokes drawing on Lewis's own academic expertise. If you know your Latin you'll see why Dr Cornelius teaches from a grammar book by Pulverulentus Siccus. If Old English is your bag then you'll know why one of the lords who flatters and betrays Miraz is called Glozelle.

Born in Belfast, Clive Staples “Jack” Lewis (1898-1963) taught English at Oxford. And the magic of Narnia is still there. The house he lived in at Headington is now a renowned chiropractic practice. And in Holy Trinity church at Headington Quarry there is a “Narnia” window by Sally Scott installed as recently as 1991.

Prince Caspian by C.S. Lewis
HarperCollins, £5.99 Buy the book here

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