Donald Trump takes it as read that any criticism of his words or actions is an assault on the truth. The historian Tacitus, who had served Roman emperors in high office (including as consul), recognised the frame of mind and reflected on how one could maintain one’s honour working for such a monster.

Tacitus saw that absolutism lay at the heart of the imperial system. To maintain it, the emperor surrounded himself with men who owed loyalty to no one but himself, and over whom he could therefore exert total control. The result was a culture of acquiescence in whatever the emperor wanted, well exemplified by the Roman senator Sallustius Crispus, who fawned that ‘the circumstances of imperial rule are such that the accounts will come right only if submitted to the approval of one person’. Everyone knew who that was.

There was another consequence. Tacitus reported that the emperor Vitellius was so ignorant of soldiering that ‘he always had to ask someone else’. So disastrous were the results that experienced centurions decided to enlighten him. ‘But Vitellius’ close advisers kept them away, since the emperor had developed the habit of regarding good advice as disagreeable and listening only to what was pleasing — and fatal.’

This desire for the pleasing brought in its train the refusal to face facts. When Rome, under Nero, suffered a disastrous defeat in Armenia, the victory trophies which had been prematurely put up were left standing. ‘It was appearances that counted; the truth was despised,’ said Tacitus. All this added up in his eyes to the corruption of public life on a massive scale.

So how should the honourable man survive? Fight the monster head on, try to make it see sense (as the philosopher Seneca did Nero), or keep his head down for better times? Some of Trump’s advisers do offer a view of policy more balanced than that which emerges from the monster’s public ravings. That, at least, suggests there is a degree of awareness of what is at stake, for them and their country. The question is whether any will survive long enough to support Tacitus’ claim that ‘even under bad emperors it is possible for men to be great’.