Last week it was suggested that the questions asked of London mayor Sadiq Khan had nothing to do with racism, but more with multiculturalism. As St Ambrose could have said, ‘If you live in Rome, live in the Roman way; if elsewhere, as they do there.’

Until the large-scale irruption of Germanic tribes fleeing the Huns in the 4th century AD, eventually ending the Roman empire in the West, Romans had been fairly relaxed about immigrants, temporary or permanent. Many came under compulsion: hostages, prisoners of war and slaves, this last group keeping wages low across a range of service industries. Rome itself actively welcomed foreign doctors and teachers, while lawyers, diplomats, the power-hungry and soldiers smelled advantage there.

Craftsmen, from sculptors to makers of luxury goods, flooded in, as did commodity traders (grain, wine, oil, etc). Foreign actors, dancers and sportsmen (e.g. charioteers) made Rome a top destination; so too prostitutes and peep-show artists like Gabbaras from Arabia, at 9ft 9in ‘the Tallest Man in the World’. Young men looking to make good greatly outnumbered women and the old; over time, friends and relatives joined them. London knows the feeling.

Though plenty of Romans griped about them, no foreigner came to Rome to pose a threat. Their sole purpose was to better themselves, learning the Roman way. After a generation or so, incomers were largely assimilated. In a polytheistic world, religion created few problems; the Jews, who did not fit this pattern, simply kept themselves to themselves. There were expulsions, usually caused by food shortages, but they never lasted long.

Those deemed to threaten Rome (e.g. Christians) soon moderated their tune. When in Rome, you rendered unto Caesar… or else.