It is cold, but not in a cheery, robin-redbreast kind of way. The sky is slate blue; the sun, a red ball, is slipping below the horizon, figures carrying heavy burdens trudge across the frozen water. Yet this far- from-festive painting, ‘The Census at Bethlehem’ by Pieter Bruegel the Elder, is one of the earliest — perhaps the very first — to set the Christmas story in a northern winter landscape.