Returning from supper in Bayeux to his battalion in the Normandy countryside one July evening in 1944, the artist and Welsh Guards officer Rex Whistler chanced upon a ruined chapel. There, on one of its white walls, he was moved to produce, with only some red and blue pencils and a piece of charcoal at hand, a modest but poignant Madonna and Child.

It was a moving portrait in more ways than one. Europe was aflame; five years of war had laid waste to that civilisation. Christendom, the comity of Christian nations, was itself a casualty of two world wars, put to the sword in the trenches, concentration camps and firebombed cities of Western Europe. Whistler’s own days were numbered too. This mural produced on the eve of battle was, we now know, to be his last.