King Canute has had a raw deal from history. He took his throne down to the beach in order to show his servile courtiers that not even a king could control the waves (that was in God’s power alone). But, ironically, he is now most often remembered as the silly old duffer who got soaked on the seashore because he thought he could master the tides. When, for example, Ryan Giggs tried last year to use a super-injunction to stop the swell of news about his private life, he was hailed as ‘the King Canute of football’.

For Aloys Winterling, the Emperor Caligula offers another case of the Canute problem. He has generally gone down in history as a mad megalomaniac: so mad that he gave his favourite horsea palace, lavish purple clothing, a retinue of servants, and even had plans to appoint it to the consulship, the highest political office below the emperor himself. In fact (so Winterling argues) his extravagant treatment of the animal was a pointed joke. Caligula was satirising the aims and ambitions of the Roman aristocracy: in their pursuit of luxury and empty honours, they appeared no less silly than the horse.

Caligula occupied the Roman throne for just four years, between 37 and 41 AD. He was the son of the glamorous imperial prince Germanicus (who died in mysterious circumstances in Syria in 19 AD), and spent much of his childhood on military campaigns with his father. Hence his name: although he was born Gaius Caesar Germanicus (and his official title