However, it looks as if consciously confining herself to these rules of engagement has allowed Mosse's imagination to leap in other ways.

At one point Alaïs's hair is described as being like a 'waterfall', while Marie-Cecile's eyes resemble a cat's (if, in real life, you stumbled across such peculiar phenomena you would, depending on your sense of adventure, call either the emergency services or the local newspaper at once). As these examples suggest, Mosse's writing stays firmly within the conventional paradigms of popular historical fiction. The other wicked woman is Alaïs's sister, Oriane, who is not only raven-haired and curvy, in contrast to her sister's airy fairness, but also sleeping with her husband, Guilhem (and not for nothing is Marie-Cecile's part-time boyfriend, who turns out also to be an old contact of Alice's, called Will).

The baddies, meanwhile, include Marie-Cecile, a French businesswoman who is after the books and who you know is evil because she wears sophisticated linen two-pieces that never seem to crease, despite the sweltering heat. It is a testimony to Kate Mosse's control over her material that the two narratives never seem to repeat or collide or, indeed, swamp one another. As Alaïs and Alice become increasingly involved in preventing the books falling into the wrong hands, their adventures echo, qualify and extend one another's as if they were playing the same orchestral piece on slightly different instruments. The job of heroine is split between the 13th-century Alaïs, the daughter of one of the leading men in Carcassonne, and Alice, a contemporary British woman who has managed to inveigle her way on to a local archaeological dig as a way of spinning out a lacklustre summer. What really marks Labyrinth out is the fact that all the main roles - goodies as well as baddies, historical and contemporary - go to women.

Kate mosse author labyrinth