It's her imagination that makes her matter. Severely disabled as a result of Stills disease (a form of juvenile arthritis), she'd spent her childhood in and out of hospital suffering recurrent painful surgery. She didn't go to school and was educated by her mother. She was cut off from the present as lived by her contemporaries in the late 1920s and early 1930s, but there was always the past. She could live out her dreams in old stories, old books. Later, writing in longhand with arthritic fingers, she would make a living from those old stories and lead others to do the same.
Manda Scott is one. When she was nine or 10, the Glasgow-born historical author picked up a book at her local library – Rosemary Sutcliff's The Eagle of the Ninth. She didn't want to give it back. "It sounds over the top but it did genuinely change my life," Scott says. It wasn't so much Sutcliff's vision of the Romans that snagged her as the Britons in the story. "I hadn't read anything that made the native Britons anything other than hide-wearing barbarians. And what really, really got me reading the rest of everything she'd written was that you knew something went on in their huts, but you never quite got to know what it was. I actually wrote the Boudica series to find out what happened when the goatskin curtain fell down. I'm writing now because of the questions she set up."
Scott's is not a unique authorial origin story. Ben Kane, author of the Forgotten Legion trilogy and novels about Spartacus and Hannibal, tells a similar tale of Sutcliff's abiding influence. Growing up in Ireland, he also read Eagle Of The Ninth and was much taken by her vision of Roman Britain. "I always wanted to see Hadrian's Wall because of that," he says. Years later, while working as a vet in England, he volunteered to assist during the foot and mouth crisis. He was sent to Northumberland and saw the wall for the first time. He immediately went out and bought a copy of Eagle of the Ninth, read it again, read the rest of Sutcliff's Roman trilogy, The Silver Branch and The Lantern Bearers, and decided he was going to write about Roman soldiers.
This is Sutcliff's legacy. This and more than 60 books, many still in print, that open a window to our past, the people who lived there and the stories they told. This month sees a new edition of Sword at Sunset, Sutcliff's epic 1963 version of the Arthurian story that dispenses with the Round Table, the gleaming armour, the magic. It's a dirty realist vision of a Dark Ages leader fighting to maintain the fading light of Roman civilisation against the encroaching Saxons. It's a vivid, violent, grown-up story that leaves you with the smell of blood in your nostrils and the chill of winter burning cold on your fingers.
"Compared to all the other books on Arthur, hers is far and away the most grounded," agrees Manda Scott, "and therefore the most real." And perhaps also the most human. "It's fascinating," suggests Kane. "She was profoundly disabled, essentially wheelchair-bound and never married or had kids and yet she had this extraordinary ability to describe things she could never have experienced. The Lantern Bearers and Sword at Sunset have an emotional depth that's quite extraordinary."
For Scott, Sutcliff doesn't quite reach the heights of someone such as Mary Renault, whose account of Alexander the Great, Fire From Heaven, is, she says, one of the greatest books ever written. But, Scott suggests, Sutcliff was way ahead of her time, and her novels planted so many seeds. "I give talks and mention Eagle of the Ninth and the entire audience goes 'oh yes'. I've never found an entire audience going 'oh yes' when you mention Henry Treece. There was something iconic about what she wrote."
It's ripe then to be rediscovered, and there's an audience to do the rediscovering. Historical fiction has undergone something of a renaissance in the past decade, Ben Kane points out, led by the likes of Conn Iggulden and Manda Scott (who writes as MC Scott) herself, perhaps inspired by films such as Gladiator. "When I first proposed my series on Boudica," adds Scott, "the publisher I was with at the time said 'we'll publish it to keep you but history doesn't sell'. Nobody is saying that now."
By reading Sword at Sunset you can perhaps see why. Published in 1954 and set more than 1500 years before, it's first and foremost about ideas of Britain and Britishness. A Britain that, back then, did not include Scotland.
"For me, if historical fiction is not giving you a lens to see the times in which you live, then there's no point in writing it or reading it," says Scott. "That's what history is for – to give you that lens." That's what Rosemary Sutcliff's work still does for us. It brings the past into focus.
Sword at Sunset by Rosemary Sutcliff (Atlantic Books, £16.99)