STANDING in the woods on Hampstead Heath early one morning, the dew still wet on the grass, Celia Rees shivers.

“I can just imagine waiting here for a carriage to pass, the sound of horses' hooves clopping,” she says dreamily.

What thunders past us on the way back from Kenwood House is a group of anoraked dog-walkers rather than the 18th-century highwaymen of her imagination. Or rather, highwaywoman, because Rees's latest novel, Sovay, is about the high-born heroine of a ballad who dresses in men's clothes to rob her true love.

In the ballad, he refuses to give up the diamond ring that is a “token from my sweetheart”, who gives him back his gold and watch and says that she would have “shot you dead” if he'd given her back her ring. In the novel, however, Sovay's fiancé is a cowardly, greedy young man who gives up everything and loses the headstrong, beautiful heiress in consequence, plunging her into a new life as a highwaywoman in England and revolutionary France.

“I've always loved that ballad; it's a little jewel of a story,” Rees says. “You can see it all - the girl, the lover, the garden, it has a strong line of passion. You know that Sovay would have shot him dead if he'd handed her ring to the “highwayman”. My friend the novelist Susan Price said to me: ‘You should write about her.' So I did.”

Rees's speciality is depicting strong, captivating heroines in a historical setting saturated with adventure, romance and emotional intelligence. Her bestselling Witch Child was one of the first and best of what is now an established genre, describing how a young woman leaves Puritan England for America; her Pirates! is about the daughter of a merchant who runs away with her black slave so that they can become female pirates.

Sovay is a gorgeous, breathless, headlong romp of a read, whose heroine takes on every challenge of the period, from being captured by a Gothic villain to being incarcerated in the notorious Conciergerie prison hours from execution at the guillotine.

The French Revolution is very much in vogue at present, with Sally Gardner's The Red Necklace and Julia Golding's Cat Royal series taking many of the same tropes.

“It's just serendipity. I suppose it's an iconic time, when the world changed. There are very few moments when time almost stopped and started again,” Rees says. “It's when human rights and women's rights and everything that now makes the modern world began. It's so rich in stories that everybody could write about it, and their novels would all be different.”

After teaching English in comprehensives in Coventry for 17 years, Rees's own talent grew out of her passion for analysing children's authors such as Alan Garner, Ursula le Guin and Robert Cormier, as well as consummate stylists such as Margaret Atwood, Annie Proulx and Angela Carter. Rees conceived of Witch Child and its sequel Sorceress after visiting the American museum in Bath, but her position as one of our leading historical novelists for young adults came about in the teeth of the received publishing wisdom of the time, which decreed that historical fiction was dead in the water.

She was so depressed by this that she didn't even show her manuscript to her agent, and she thought it would never be published. But then Bloomsbury's children's editor, Sarah Odedina, while on holiday noticed the monument put up to the last woman burnt in Scotland as a witch and asked agents whether any established authors might be interested in writing a novel about this.

“I think she was a bit surprised when my synopsis and four chapters appeared, as if by magic,” Rees says, laughing. By then, she had been writing fiction for young adults for a decade, and after 12 books had “served my apprenticeship”. Witch Child was her breakthrough book, sold to nine countries, and began the new wave of historical fiction for young adults that Susan Price, Elizabeth Laird and Nicola Morgan, among others, took up with brilliance and vigour.

It remains one of the most enthralling and empowering novels for girls of 10+ to encounter, though Pirates! (which anticipated Pirates of the Caribbean) runs it a close second. Each heroine, she says, “grows out of the last one”, and bold, brave, passionate 17-year-old Sovay, brought up on Rousseau's Social Contract, is such a handful that the underlying quest of the story is to find her a man who is, as her author puts it, “big enough to take her on”. When she finally meets Leon, a Gérard Depardieu-like French aristocrat who has joined the revolutionary side, the attraction is satisfyingly instant and mutual.

Having read politics and history at Warwick University, she is well placed to research her tales; the phenomenally evil villain Dysart, who Sovay must outwit, has a castle based on the vanished Fonthill Abbey. Although its Illuminati ritual, imprisoned child prostitutes and proposed sacrifice of Sovay are piled on as fantastic extras, the realities underpinning the fantasy are impressively meticulous.

“I got incredibly excited finding a place that fitted what I'd imagined so exactly,” Rees says. She is exactly the kind of person who would have been an inspirational teacher, because her enthusiasm is infectious; a tomboy as a child in the now-vanished fields around Birmingham, you suspect that quite a lot of Sovay's strong will comes from her author. And as in the days when the adventures of the Scarlet Pimpernel thrilled generations, modern teenagers' access to this fascinating period will again be through fiction.

“I do far more work for my novels than I did researching my degree,” Rees says, ruefully; but if a new generation of readers get turned on to the ideas and personalities of the past as a result of novels such as Sovay, then it's time well spent.

Sovay (11+) by Celia Rees
Bloomsbury, £10.99; 416pp
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