Eighty years ago this month a young bloke from south London called Wally Parr was floating through the night in a flimsy wooden glider a few thousand feet over the Channel. He wasn’t alone. Jammed alongside him in one of six such craft were his mates from the British army’s 6th Airborne Division. On the night before the D-day landings, they were heading behind enemy lines to capture a bridge from the Germans. Some wouldn’t see the dawn. If the 181 men on these gliders were afraid, adrenaline and delusion may have helped still their nerves. “The thing that keeps...