The Valley of Secrets. By Charmian Hussey. Illustrated by Christopher Crump. Hodder Children’s Books pound;12.99

When we plunge into the strange realm of fantasy literature for children, our one prerequisite is that the author accompanies us. Here is Lewis Carroll, twinkling merrily around the corners of Wonderland; here J K Rowling, holding hands with Harry; here Philip Pullman, wondering with Will, urging on Lyra. Here too, though possibly on a less exalted plane, is Nancy Farmer, thoroughly involved in her half-history, half-make believe AD 793, when Viking raiders decimate Christian British villages (true) and are involved in wars with trolls and monsters (fictional, but drawn from the fiction of the period).

Such a stew of period detail - honeycakes and barley bread; sooty hearths and swift-oared Dragon boats - makes a great growing medium for a story that features an 11-year-old boy hero, shape-changing, wizardry, a quest into an icy land of magic where nothing is what it seems and a wholesale importation of the cast of Beowulf.

It’s as if what really happened (Viking invasions) has been melded with what people were telling stories about (monsters, wizards and giants).

That these things are always in close relation, Tolkien, among others, demonstrated in his essay on “Beowulf, the monsters and the critics”: we have the fantasies which express our feelings. As Sea of Trolls is a child’s fantasy, of course, there is a happy ending, but that’s all to the good. Magic doesn’t work except in books.

Charmian Hussey’s charming novel, dug out of an attic after 17 years, self-published and now adopted by a mainstream publisher, tells the story of an orphan who inherits an estate in Cornwall - an estate with a secret.

The story twines together a teenager’s discovery of his own strengths and a parable about exploration and conservation in a manner more reminiscent of the 19th than the 21st century.

In fact, the narrative is interspersed with Victorian diary entries as well as reassuring comedy with local rustics and nice detail about scratch meals from cans and bottles, all of which is delivered in a tone both adult and interested: a bit like going for a walk with your favourite aunt. Stephen, the hero, is not really a recognisable child or adolescent male despite his penchant for rich tea biscuits - rather, he is the vehicle for the reader to enter a natural world of imaginative richness.

This friendly fable is exquisitely illustrated by Christopher Crump, maps and all.