‘What,’ asked my husband teasingly, by way of an early Christmas game, ‘connects wolf’s-bane with Woolwich Arsenal?’ It took me a little time, but I got there via aconite.

Ovid put its origins most vividly. When Cerberus was dragged by Heracles from Hades, triply barking as the steel chain was twisted round his necks and averting his eyes from the glare of day as he came up through a cave on the shore of the Black Sea, the monstrous dog dropped slobber on the ground, from which grew the poisonous flower aconite.