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The fine new exhibition at the British Museum, Moctezuma, is a reminder of one of our most fondly held stereotypes: the noble savage confronted by the cruel Spanish conquistador.

Neil Young put it succinctly in his song Cortez the Killer, in which Cortés is met by a New Age Moctezuma (also known as Montezuma) surrounded by beautiful subjects offering coca leaves and pearls: “Hate was just a legend and war was never known.” This was the paradise that the brutal Cortés supposedly destroyed.

The Spaniards did, of course, bring both guns and germs to the New World, with devastating effect. The Aztecs — or more properly the Mexica — were an advanced and sophisticated civilisation. But any appraisal of their empire has to deal...