By his own admission, some of novelist Philip Pullman’s fans are as young as seven, but that hasn’t stopped him littering a prequel to his bestselling series with swear words.

La Belle Sauvage is set ten years before the author’s acclaimed His Dark Materials trilogy, and is Waterstones’ biggest pre-order title since Harry Potter And The Cursed Child.

Fans of the trilogy, which sold more than 17.5million copies worldwide, have been eagerly anticipating the new novel following a 17-year gap.

But the use of explicit language throughout – including the f-word as well as bloody, b*****ks and b*****ds – could see younger fans forced to wait a few more years before their parents allow them to dive in.

Philip Pullman's new prequel to his hit series His Dark Materials contains some strong language in the excerpt which may turn off some of his younger readers

When the 71-year-old was asked at the launch of the book how many swear words he had used, he said: ‘I don’t know, perhaps we ought to have a little excerpt on the front which says “swear words on page... watch out”, or “swear word approaching”. ’

He added: ‘I’ve got older too, and perhaps more cynical and closer to despair and all those sorts of things. It is a darker book, I can’t deny that, but that’s the story that came to me and wanted to be told.’

The novelist refuses to label his books for specific age ranges. He said: ‘I don’t specify my audience because I’ve never wanted to do that. I’m very grateful to have any audience at all, and to say this book is for 12 to 14-year-olds limits it rather than welcoming people. I want to welcome in as many readers as can possibly be interested in the book.’

Pullman has previously revealed he receives letters from fans as young as seven. He told the Daily Telegraph: ‘They have read all the way through His Dark Materials and they have an astonishing knowledge of it. But not every child is the same. The book should be suited to the individual child.’

La Belle Sauvage is the first novel in a trilogy named The Book Of Dust.