We all know the true story of how Father Christmas came to be. It was the work of Siberian shamans high on magic-mushroom-infused reindeer urine climbing in and out of the smoke holes of their yurts, dressed in red-and-white costumes inspired by the distinctive colours of their drug of choice, the Fly Agaric mushroom.

The sad thing is, Andy Letcher tells us in Shroom, this is just another of those legends concocted by hippies to give their recreational drug use a bit more historical and cultural depth. In fact, even before they were exterminated by Stalin, hardly any of Siberia’s shamans used Fly Agaric; none of them wore red and white; they didn’t use sleighs; and they never drank reindeer pee. (Though it’s true – at least according to an eighteenth-century Swedish colonel named Philip von Strahlenberg – that the peasants of Siberia’s Koryak tribe would gather outside rich people’s mushroom feasts and wait for the guests to come outside to relieve themselves so that they could collect the hallucinogenic wee-wee in wooden drinking bowls and enjoy a free trip.)

Nor – despite what New Age travellers might like to think – is there any evidence that the Druids took magic mushrooms. And the notion that the ancient Greeks imbibed them during their secretive Eleusis celebrations (the disclosure of whose mysteries