After a summer of gold, silver and bronze, and political leaders the world over who, as master reverse alchemists, offer their people the lead of inadequacy rather than the precious metal of leadership, let us now speak of diamonds — a topic favoured by us economists for centuries.

On Thursday, the president of Botswana, adorned with the alliteratively magnificent moniker of Mokgweetsi Masisi, unveiled the second largest diamond ever found. It filled his hand and weighs more than a pound — an astonishing 2,492 carats.