Injured terribly during a skirmish with natives flamed to rebellion by a wandering druid, he must forfeit his military career. The Eagle of the Ninth tells of the young Marcus Aquila, a centurion on his first command on the fringes of the Roman empire. That and the mysterious fate of the Ninth Spanish Legion, which, having been quartered at York, apparently vanished from the historical record in the early years of the 2nd century.

And it was this bronze eagle from which Rosemary Sutcliff made her children's story The Eagle of the Ninth. There are so many unanswered questions in ancient history, questions that the novelist, where the historian may tremble to advance a theory, may joyfully answer with invention. A mystery: how had this creature, which Joyce thought must be an eagle from a Roman legionary standard, ended up here? In 1866, when the superbly named Revd James Joyce was excavating the Roman town of Calleva Atrebatum, near Silchester in Hampshire, he found the eagle buried beneath the town's basilica.

He is also about the size of a pigeon and lacking wings, such that his grandeur is a little undercut by melancholy, even bathos. His beak is cruelly curved, his feathers exquisitely described in the surface of the dully glowing metal. I n Reading Museum – among tantalising treasures including a silver spoon declaring itself to be the property of a long-lost girl called Primania, and a roof tile into whose not-yet-dry clay someone scratched half a line of Virgil's Aeneid – is a little eagle cast in bronze.

The eagle of the ninth