‘Racism’ refers to the belief in racially determined inferiority, most often recognised in body-type, about which, by definition, nothing can be done. It is hard therefore to see why accusing London mayor Sadiq Khan of sharing platforms with terrorists was ‘racist’. It was simply a comment on the company he kept.

The ancients are often accused of racism. The Roman architect Vitruvius, for example, said that southerners living in hot climates were intelligent but cowardly, while northerners were mentally slow but brave to the point of foolishness. Obvious racism? Far from it. A Greek doctor, following the same train of thought, gave the game away. He asserted that in Asia ‘men will be of fine physique, tall, differing little from one another, but courage, endurance, industry and high spirits are impossible to find among the natives and immigrants’. Note ‘immigrants’: they were clearly not of the same racial stock as the natives. And that was the whole point: it was living there that made you what you were, not your heredity.

In other words, for ancients it was not your body type but your culture — behaviour, customs, habits, life-style, associates and so on — that formed you. Live in a different culture and you became different. Live like a Roman and you became Roman. Roman emperors from North Africa, Spain and the Balkans, many speaking pretty rough Latin, would agree. This was well in line with Aristotle’s view that, whatever your beliefs, what counted was your behaviour — what you said and did — and that was entirely within your own power to determine, because it was a matter of your own choosing.

If, however, you choose not to do in Rome as the Romans do, it is bound to attract attention which may be critical, demeaning or insulting. That may be unpleasant but is not thereby ‘racist’; indeed, it might be justified, which racism cannot be. And so to Mayor Khan. For one born in Britain, being on apparently friendly terms with religious and racist extremists is not quite the British Way.