On retiring from office, Boris Johnson described himself as a sort of Cincinnatus, returning to his plough. This famous story attracted two comments from the media, both missing the point.

According to the historian Livy (c.59 bc-17 ad), when Rome’s last king, the tyrannical Tarquinius Superbus – ‘the arrogant’ – was ejected in 509 bc, those who had acted as his advisers (patricians, i.e. senators) assumed control. But conflict soon emerged between them and the plebians over problems of freedom, poverty and debt. By refusing to co-operate with the senators, especially by refusing to wage war, the plebs eventually won the right to appoint tribunes from among their number to try to solve the problems in the plebs’ interests, with mixed success.

In 458 bc Rome found itself in serious military trouble – so serious that even the plebs realised the safety of Rome was in doubt. So despite the tribunes’ protests, two armies were raised, and a filthy, sweating Cincinnatus was summoned from ploughing his three-acre farm – or was it digging a ditch? – to put on his toga and appear before the senate. He was given total power as dictator for six months to deal with the crisis. It took him 15 days to defeat the enemy, at which point he went back to his farm and resumed ploughing (or digging).

On the Today programme, Dame Mary Beard said that the ‘sting in the tail’ was that Cincinnatus was no lover of the poor. But how is that relevant to the story? Others pointed out that in 439 bc Cincinnatus was again called out of retirement, much against his will, to deal with what was described as a potential coup, namely someone bribing the poor with free grain (presumably the explanation of Dame Mary’s ‘sting in the tail’). Was this, then, the implication of Mr Johnson’s reference, that he would at some stage return? But even if it was, Cincinnatus still resigned again, this time after 21 days. So that does not work either.

This tale is what Romans called an exemplum: a story from the past useful for discussing moral problems. So what did Mr Johnson mean by it? Does it even fit him?