ROBYN Young is trying not to look exhausted. She is halfway through a two-week marathon tour of Scotland on the trail of Robert the Bruce. Via crumbling castles and ancient battlegrounds, she and her Mini have reached Aberdeen, once home to John of Strathbogie, one of Bruce's closest friends, and a brief respite in a hotel.
"Half of you is driving in a car and seeing other cars, and the other half is trying to put yourself constantly in this other world," says Young, who is now working on the second book of her trilogy about Robert the Bruce - the first, Insurrection, is published this month. "You can't just sit there and enjoy the scenery, you have to constantly be on top of what you're seeing, what they would have seen."
Not only is she having to bridge a time gap of some 700 years, she is dealing with a hero who made his mark on much of his country, whether as warrior, fugitive or king. "Pretty much every place I go, he was there - and many places that I can't get to in a single trip. That's one of the interesting things about him, he covered so much ground, and what he started rose to sweep the whole country, everyone at every level became involved."
Young, who lives in Brighton, is being hailed as an important new voice in historical fiction after her trilogy about the Knights Templar, Brethren, Crusade and Requiem, which have sold 800,000 copies between them in the UK alone and have been translated into 19 languages. Her Templar hero is a Scot, and during her research she happened upon Robert the Bruce, the most enigmatic of leaders in the Scots Wars of Independence, a man "too powerful to be a cameo in another man's story". His tale had been told before, of course, not least by Sir Walter Scott, but she felt he was a particularly resonant figure for a modern audience.
In recent years, Bruce has played second fiddle to the man with whom he shared a historical stage, William Wallace. "Robert fell out of fashion at some point, and the more I read about both of them I thought: 'How is this possible?' Robert is such a fascinating, changeable, unpredictable man. He's very driven, very ambitious, and yet he remains very likeable. He has a lot of flaws, but I think today people are more drawn towards flawed characters.
"I totally understand why Hollywood took Wallace on because he's a very black and white character. He stays very true to this one cause and fights for it until he dies. Braveheart compared Bruce to Wallace, you have to do that in Hollywood, but they're both extremely powerful in their own right, both had characteristics which set them apart from other men. For me Robert is by far the more interesting, the one who changed a lot more."
While Braveheart portrayed Bruce as a turncoat, even a traitor, the reality seems to have been much more complex. He and his father did fight with Edward I of England against the Scots, but in 1297 Robert defected to the Scottish side. He later submitted to Edward along with most Scottish nobles (Wallace being a notable exception) but in 1306 shattered the fragile peace between the two countries by murdering his arch-rival John Comyn and asserting his own claim to the Scottish throne.
No sooner was he crowned than he lost in battle to the English and was forced to flee to Ireland (where he may or may not have been inspired by watching a spider in a cave), while terrible acts of vengeance were visited on his family. He clawed his way back in a guerilla war and re- established Scotland as an independent kingdom. It was under Bruce that the Declaration of Arbroath, the seminal statement of Scotland's right to nationhood, was signed.
For a writer, Young says, it's the perfect story arc. "He fulfils his ambition, he becomes king, and then everything falls apart for him and he's left with this small band of men and his wits. He loses everything and he's clawing his way back up, but that's when I feel he really comes to know himself. And you get at the end of that someone who is a really good king."
Even in this opening segment, Young doesn't shy from the brutality of the medieval battlefield, or the Byzantine politics behind the conflict. The Scottish court is a hotbed of rivalries and relations with the English are complex. Edward I dreamed of uniting the British Isles under a single banner like his hero, King Arthur, and many Scottish nobles had loyalties in both camps. This turbulent period forged elements of the political landscape we know today.
"This is the point where what we know as the British Isles, with all of its politics in terms of emnity and strength of feeling, is forged. That's why I find it so fascinating, and why I think it's crucial that it's told in an accessible way. My family is very British, I have Scottish, Irish and Welsh blood. It's about being aware of where you come from."
Like all historical novelists, Young must weave her story around certain firm facts using imagination when historical records stop. It means being immersed in background knowledge and period detail, but not being afraid to take occasional liberties in service of the narrative. "It's a lot of responsibiity, because I do take the history very seriously, and I'd like it to be plausible even where we don't know (exactly what happened]. You've got these little islands of knowledge, and you have to build a bridge between each one and join them up, hopefully into one big land mass which is a bit more easily traversed."
Young is one of very few women writing swashbuckling historical adventures - her pseudonym was deliberately chosen for its gender ambiguity and she admits she spends much of her time in a man's world.
"I wouldn't be interested in writing romance or saga, that feels quite claustrophobic to me. Women, particularly in the Middle Ages, were confined by their sex to a smaller existence. I think I would find that really hard, I need to be where the men are, able to control more of this world that I'm writing about."
Young was, she says, a bit of a tomboy, an only child who escaped into books and grew up loving adventure narratives - Susan Cooper, CS Lewis, Pat O'Shea's The Hounds of the Morrigan. "I spent some of my happiest moments in childhood at my grandparents' house in Somerset with my cousins. We'd sit around in one bedroom in our pyjamas with cocoa and my grandfather would tell adventure stories in which we were all the main characters. It was idyllic to the point of Enid Blyton!"
She spent her teens convinced she would become a journalist until someone she met in the profession warned her that she was "too nice". "And that put me off, but it also made me realise that I'd compromised, I'd gone for journalism because I thought that would be a way of earning a living and still working with words, but what I'd always wanted to do was to be a novelist."
Deciding not to go to university, she drifted, hitching to Brighton where she ended up helping to run a music festival, then a nightclub. Finally, in her early twenties she took a "grown-up job" in a building society, which she hated so much it made her ill. But she also wrote a 350,000-word fantasy novel in six months. "It was the first of a series, I wrote two, they were pretty dreadful but they were just something that had to come out, I think, before I could do anything good or real."
She was signed off sick with agoraphobia when she first came across the Knights Templar (in the days before The Da Vinci Code, they were a minority interest at best), saw a trip to Egypt advertised and promptly booked it. "All my friends and family said, 'You've hardly left the house for six months, how are you going to get on a plane?' And I said, 'Well, I think it's probably going to be kill or cure'. And it turned out it was cure. It was a huge culture shock, a whole new perspective, a really good kick up the backside, actually." When she returned, she quit the building society and enrolled in an evening course in creative writing, on which she wrote the first draft of Brethren.
It took seven years and 11 re-writes before Brethren became the subject of a bidding war between two major publishers, and became the UK's bestselling hardcover debut of 2006. Post Da Vinci Code, the Templars were hard currency among publishers, but the growing audience for books by Young, C J Sansom and others have proved that there is plenty of mileage in the historical epic.
Almost overnight, Young went from being unknown and unpublished to seeing her book sold all over the world.
"It's been a big life learning curve," she says. "You get faced with a lot of challenges you're not necessarily expecting. When I was published in the US, they asked me to do a coast-to-coast radio tour from my own living room in Brighton - 18 interviews in six hours and half of them were live, and I'd never done a radio interview in my life. I remember the first one, my little shaky mouse-like voice on the line to North Carolina, and by the end of the day it was 'Hello Arizona!' - I'd found my flow."
It's clear Young loves what she does, although it's no dawdle; she delivers a 200,000-word novel per year. "I think one reason I became a novelist, particularly a historical novelist, was that sense of learning a secret, because so many people don't know these things, and then having this wonderful vehicle to tell everybody this secret, to share your own excitement with readers. Robert the Bruce is a good character for us to get our teeth into. He did go out of fashion. Now, in our complex world, I think it's time for him to come back."
• Insurrection by Robyn Young is published by Hodder & Stoughton on 14 October, priced 17.99. She will be launching her new novel at a series of events in Melrose, Stirling, Perth, Aberdeen and Inverness through Book Nation. Full details at www.robynyoung.com/events or www.booknation.org.uk