Kate Mosse: Grail tales of girl power

"I've always been rather frustrated that there's so little adventure writing for women", says the author. "Almost all the stories I've read are very much hero-driven, with women as the handmaidens. I was keen to see if I could write an adventure story where the women get to have lovely frocks, sex and swords and don't wait to be rescued."

It's unsurprising that Mosse has two headstrong heroines - 13th-century teenager Alais and contemporary 30-year-old Alice - at the centre of the plot. A minute in Mosse's company and you feel the energy radiating from her. Her diary must be as action-packed as her novel. In the autumn she'll be stepping in for Mariella Frostrup on Open Book while continuing to present BBC Radio 4's Saturday Review. September sees her chairing the Best of the Best award celebrating 10 years of the Orange Prize for Fiction, which she helped co-found and continues to promote.

The first person in her family to go to university, Mosse has remained a staunchly local girl. She and her husband met at school and live near Bognor Regis; her grandfather built the local church. Her parents are in the next village; her sisters live nearby too.

Until she went to New College, Oxford, Mosse's obsession was music. She played the violin and piano. Did she also spend her childhood writing? "A couple of years ago I was interviewed and said that I never wrote. After that I got letters from people I'd been at school with saying, 'Are you mad?' You were forever writing plays and forcing us to be in them' And my mother said, 'You were always writing novels. You wrote that awful series about Eskimos!'" Mosse laughs. "I had in my mind that my vocation was as a reader. I just love reading."

One author she discovered in her teens was Agatha Christie, who gave her a love of crime. "I re-read Agatha Christie every year, and Ngaio Marsh too." In traditional detective stories there's a reason for everything. "It's a self-contained world where the moral order is put out of joint and then restored at the end. In contemporary crime fiction people are killed because they are in the way, but with adventure stories mostly the people who find themselves coming a cropper are baddies." That's certainly so in Labyrinth. Villains vanish into bogs, get shot at or hit by speeding cars. But even the heroines get bashed about along the way as they dash in and out of danger.

"Almost the biggest character with no lines is the landscape," says Mosse. Carcassonne, where she has a second home, inspired much of the story. "In that part of France the spirit of place is very strong." Mosse and her husband bought their house in the shadow of the city walls, 16 years ago. This is where Mosse likes to write. Up at four in the morning, she works for about 10 hours a day. "I don't need an enormous amount of sleep. I'm pretty happy on six hours."

Various interests led to the book's genesis. Mosse became fascinated with the history of Carcassonne as a Cathar stronghold. A Christian sect, Catharism had enormous sway in the region from the late llth century until the early 13th century when the Inquisition was formed specifically to stamp it out.

"It was a rival to the Catholic church", explains Mosse, "a most modern religion in a way. There's an emphasis on the word and on communication directly with God. The Cathars had no possessions and believed in reincarnation. They were dualists who believed that God is the god of heaven and the devil is the god of the earth. Catharism is based on equal and opposing forces." In this tolerant faith, which offered universal redemption, some of the priests were women. It suggests a degree of female self-determination unthinkable elsewhere in medieval society. In Labyrinth - where the one hitting the Grail trail is a girl - Catharism offers plenty of potential for adventure.

One of Mosse's favourite novels as a child was Rider Haggard's She, about a princess who stays forever young. "This must have played a big role. I've always been interested in knights and partial to swords", admits Mosse, who mentions that her family coat of arms was supposedly won at the Siege of Acre. She feels that the origins of the Grail with its promise of eternal life could be pre-Christian. There's no reference to it in the Bible. "It appears almost out of the blue in Chretien de Troyes in the 12th century, in the poem 'Joseph d'Arimathie' by Robert de Boron and in 'Parzival' by good old Wolfram von Eschenbach. They all said, 'I learnt this from a man on a road on a horse.' Medieval poets never claimed to have made things up themselves."

Mosse's research took several years. Labyrinth's complicated story zigzags back and forth between past and present. Writing both narratives in full, Mosse then cut about half so that her story flowed and she didn't repeat herself. She decided too to sprinkle in Occitan words and phrases. When the northern French crusaders conquered the rich lands of Languedoc - supposedly to eliminate the dissidents, but also to gain their territory- it was a turning point. Occitan (the language of the Midi and also of Christian Jerusalem) was eradicated. In Labyrinth, therefore, the bad guys speak French and the good guys Occitan.

Dan Brown's blockbuster appeared in bookshops just as Mosse finished her first draft. Was that a blow? "No. I read The Da Vinci Code before starting the serious editing on Labyrinth. It's a terrific read," she says. "Both have the idea of the Grail at the centre but Dan Brown's is the traditional Christian Holy Grail and mine is not. I wanted to put across the idea that the three monotheistic religions are at war with one another but actually the principles of belief are remarkably similar. People say, 'Do you worry about being compared to Dan Brown?', to which the answer is, 'If my book has a tenth of his sales...!"

Yet Mosse claims she didn't consciously choose to write a commercial novel as opposed to a literary one. "I really dislike those distinctions", she says firmly. "I feel that books are either good of their type or bad." Mosse, who naturally finds herself thinking in terms of cliffhangers and coincidences, planned "to write something that moves very fast with the story and characters driving it. I wanted people to say they couldn't put it down."

If Mosse's literary novels are like chamber pieces, Labyrinth - weighing in at 525 pages - has an orchestral feel. She warms to the comparison. "If you listen to Shostokovich's fifth symphony, the third movement has a layering of different voices, an interplay of rhythm and texture. A symphony works because the story goes backwards and forwards. With Labyrinth it felt like layering too. It was enormously satisfying."

Books like The Da Vinci Code demand a succession of revelations and frequent scene setting, making them top-heavy with information. Novelists who have done their research and know the dimensions of every building and the origin of each religious symbol seem unable to resist sharing it with the reader. "If you're aware of being given information, possibly the author hasn't pulled it off at that point", Mosse says, thoughtfully. On the other hand, fans of the genre do seem to love learning things and they won't be disappointed here.

Mosse felt that getting the history right was crucial. But she was also writing a love letter to Carcassonne. "The very first time I went there I felt utterly at home. That blue of the Midi sky...When I sit writing, what I see from the back of my house are the lices (grassy slopes) of the cite. Every August I go up and watch the joust. I don't mind the plastic swords. I love it."

Biography: Kate Mosse

Born in 1961, Kate Mosse was educated at Chichester High School for Girls and read English at Oxford. She started as a secretary at Hodder and Stoughton and went on to become editorial director of Hutchinson. Leaving to write her first non-fiction book, Becoming A Mother, she helped co-found the Orange Prize for Fiction and remains Honorary Director. Her other books include The House: Behind The Scenes at the Royal Opera House, Covent Garden and three novels Eskimo Kissing, Crucifix Lane and most recently Labyrinth. She was the first ever woman Executive Director of Chichester Festival Theatre and presents BBC Radio 4's Saturday Review. In 2000 she was named European Woman of Achievement for Contribution to the Arts. Married with two children, she lives in West Sussex and in south-west France