The behaviour of people in crowds is rather different from that of the same people in the privacy of their own homes; so much is obvious. But it was the French doctor, writer, and all round intellectual Gustave Le Bon (1841-1931) who was the first to consider the difference at book length. His Psychology of Crowds, published in 1895, was a founding text of social psychology.

Le Bon is usually said to have qualified as a doctor in Paris in 1866, though some have disputed whether he ever passed his baccalaureat, let alone his doctorate. Be that as it may, he practised for a time and published widely on such …