Sword at Sunset, By Rosemary Sutcliff

This anniversary edition of Rosemary Sutcliff's 'Arthurian' adult novel proves it was her 'odd one out'

Rosemary Sutcliff is most famed for Eagle of the Ninth, but there was much more to her than that. In the 1950s, historically-minded children found her books a magic carpet into the past. I began with Brother Dustyfeet (1952) and The Armourer's House (1951), and never looked back an insatiable interest in history has remained the backbone of my life.

In 1954, Eagle of the Ninth introduced Marcus Flavius Aquila, a young Roman who chooses to stay in Britain after the legions leave. Seven subsequent books follow his family's fate, usually directly. The odd book out is the fifth, Sword at Sunset, now published in a new edition to celebrate its 50th birthday. In 1963, it was firmly announced to be for adults, and given the (for their time) graphic and violent scenes of sex and slaughter, it deserved to be.

It is also unusual among Sutcliff's books in that it is told in the first person. Artorius, devoted nephew of the High King Ambrosius, has a bit part in the fourth Aquila book, The Lantern-Bearers, but now takes centre stage. He recalls on his death bed how he was charged by the ageing Ambrosius with leading a crack fighting force known as the Companions against invaders from Saxony, Jutland and Norway.

In time, he becomes the High King of Britain, even Caesar Britannicus, but his doom has threatened ever since he was drugged and seduced by his half-sister Ygerna and begat Medraut, a boy filled with hate by his mother. Memories of this bedevil his marriage to Guenhumara, and she and the Gallic harpist and warrior Bedwyr (rather than Lancelot) grow perilously close.

When Sutcliff first began to consider how Arthur would fit in to her saga of Aquila, she drew as much upon the archaeology of Celtic and Saxon Britain as on the ancient legends in Malory's Morte Darthur and Guest's Mabinogion. She also admired TH White's four idiosyncratic Arthurian novels (now known as The Once and Future King), and the intensity with which she inhabits the mind of her hero Artos has echoes of White's extraordinary characterisation of Arthur. "I have never written a book that was so possessive," Sutcliff said in an interview in 1986. "It was almost like having the story fed through me". Writing as a man possessed her; afterwards, "I had great difficulty getting back into a woman's skin."

Her narrative amazes in the sheer vigour of its visualisation and its sure sense of purpose. Lanterns, sunsets, fires, the aurora borealis and other manifestations of light recur: Artos is holding back the coming of the dark long enough for there to be hope that the civilised light that was Rome will survive to be adopted by its conquerors. Battles are heart-stopping, tense and unpredictable, winter weather effects are frostbite-inducing, and Artos's travels across Britain are confidently mapped (the glossary of Roman names will be needed).

No-one would dream from reading Sword at Sunset and Sutcliff's other action-packed, fast-moving tales of Roman and Celtic warriors that she remained severely crippled all her life with the juvenile arthritis she contracted as a very small child. Once one is aware of this, a recurring theme of incapacitating wounds is better understood; as is the important role she gives to the hounds and horses in which she found such consolation.

Christian Hardyment's life of Thomas Malory is published by HarperCollins