‘Men make a wilderness and call it peace.’ If we only had that epigram from Agricola and nothing else of Tacitus’s work, it would be worth it. In its sentiment, if not its expression, it is typically Tacitean. Tacitus puts the words in the mouth of Calgacus, a British chieftain for whom there is no philosophy to extract from them – but there is for Ian Morris. Pacification, says Morris, is a form of peace, even if, as Tacitus reminds us, peace can be ruinously destructive.

Morris begins with Tacitus and his father-in-law Agricola’s victory against barbarians at the Battle of the Grampian Mountains in AD 83, a confrontation ‘at the edge of the world’. The Stoic philosopher Seneca saw the Roman Empire as a moral concept – the frontier was a moral barrier between people