367 AD. At the edge of a Roman Empire whose power is faltering under attack from without and within, lies Britain, a land rich in possibilities but drained in taxes, wasting under imperial neglect and menaced by sporadic barbarian incursions.

In Silchester, at the heart of the prosperous trading empire of his own making, Drusus Antonius Muras, a powerful, ambitious businessman, is compiling a balance-sheet. His subject is Britain: her assets, liabilities, the actual and the potential. Under the direction of the right man, a man with talents to manage, take charge, subdue, an independent Britain could astonish the world.

But at first gradually, then with frightening momentum, barbarian raids increase until Britain is facing the inconceivable: an apparently concerted invasion by Picts, Scots, Scanians, Attacots, Brigantes... They attack from all sides, swarming over the Roman defensive walls and penetrating deep into Britain. Besiged in Silchester, Drusus determines to exploit the uncertainty of the times to seize his chance.

In Three Six Seven Peter Vansittart presents Drusus' own account of that extraordinary year, one of the most momentous in the history of Britain. Charting the rise and fall if this 'very important man' he creates a novel in incident, character and style, a masterly portrait of an exceptional man at an exceptional time.