“ ‘Dad,’ he says to me out of the blue, ‘I’ve got to do my bit,’ and he shows me his enlistment papers. You could’ve knocked me over with a feather. Not that he’s not patriotic, you understand, but he’d had his little difficulties at school, sowed his wild oats, so to speak, and here he was, saying, ‘Dad, I want to do my bit.’ ”

The sirens went, taking up one after the other. Mrs Lucy said, “Ah, well, here they are now,” as if the last guest had finally arrived at her tea party, and Jack stood up.

“If you’ll just show me where the spotter’s post is, Mr Harker,” he said.

“Jack,” I said. “It’s a name that should be easy for you to remember.”

I took him upstairs to what had been Mrs Lucy’s cook’s garret bedroom, unlike the street a perfect place to watch for incendiaries. It was on the fourth floor, higher than most of the buildings on the street so one could see anything that fell on the roofs around. One could see the Thames, too, between the chimneypots, and in the other direction the searchlights in Hyde Park.

Mrs Lucy had set a wing-backed chair by the window, from which the glass had been removed, and the narrow landing at the head of the stairs had been reinforced with heavy oak beams that even Olmwood couldn’t have lifted.

“One ducks out here when the bombs get close,” I said, shining the torch on the beams. “It’ll be a swish and then a sort of rising whine.” I led him into the bedroom. “If you see incendiaries, call out and try to mark exactly where they fall on the roofs.” I showed him how to use the gunsight mounted on a wooden base that we used for a sextant and handed him the binoculars. “Anything else you need?” I asked.

“No,” he said soberly. “Thank you.”

I left him and went back downstairs. They were still discussing Violet.