How did a Catholic religious celebration transform into a spooky, supernatural festivity? Why were turnips and swedes replaced by pumpkins? And what happened on ‘mischief night’? Speaking with Ellie Cawthorne, Professor Owen Davies uncovers the historical origins of popular traditions surrounding 31 October – from the malicious and downright dangerous beginnings of trick or treating to the ethereal inspirations for Jack-o’-lanterns.