Just before closing time, I found myself alone in the gallery with this recumbent figure by Henry Moore.

It is so beautiful that it sent shivers down my spine.

I am so pleased I went back to Tate Britain to see this exhibition again before it closes, because my first visit was very crowded. And it is a rare treat to spend a few minutes alone with something so moving.

Night after night during the Blitz, Moore roamed the London Underground system, fascinated by reclining figures bedding down for the night as working-class Londoners sought shelter from the bombing, for the price of the cheapest penny ha'penny ticket. (Middle-class families had their own shelters in their own back gardens.) The trains kept running until their usual hour, so families with small children huddled to the back of the platforms to allow passengers to go by. Moore captured that pathetic vulnerability of sleeping in public; mouths dropping open, limbs contorted, as sleepers clutched their grimy shreds of blankets. He couldn't sketch openly; it would have been like sketching in the hold of a slave ship, he said. These figures seem like mummified bodies; you can almost smell the fetid air. This sketch was made at Liverpool Street, in a new train tunnel in which the rails hadn't been laid.

I go home, as usual, by Tube. I am lugging a bag of groceries, I can't get a seat ... I don't spare a thought, until I get home, for the sleepers.

It happened 70 years ago, next month.

Which doesn't seem all that long ago. When you think about it.