We had almost nothing on our walls. We rented the house furnished, but the hooks on the walls were bare. My mother had put some posters up in the back room. I wondered who the owners of the house were, what art they had had here and where it had gone. And I thought of that woman in George’s paintings, looking right at me, tugging her robe down until her breast was in full view.

Drizzle stopped our Sunday picnic plans. It came in overnight and put a wet gloss across the grass and darkened the concrete. The forecast was for more of the same for the rest of the day.

Plan B was a trip to the London Planetarium, an identical journey to the week before, since it was next to Madame Tussauds. More time on a bus in stop-start traffic.

Michael sat between our mother and me in the auditorium and grabbed my hand when the lights went down.

‘This is how they do it,’ I whispered to him. ‘They make it like night-time. Then you look up and see the stars.’

The show that day had two fifteen-minute halves, starting with ‘The Nativity’. Christmas was eight days away.

The stars came up – the modern night sky – and then whirled as we went back in time. Michael gasped and clenched my hand harder.

In front of us, now barely a shape in the dark, the huge projector shifted silently. It had a bulbous segmented body and jointed steel legs, like a giant metal insect or the alien on the cover of Jeff Wayne’s War of the Worlds album.

The narrator talked about the birth of Christ, and possible dates for it, and talked us through the constellations in the night sky at the time.

As the images shifted again, my mother leaned across Michael to me and whispered, ‘Isn’t that the most British voice you’ve ever heard? Well, that and Mr Lascelles’, perhaps.’

She was right. It was the voice of someone who played polo with Prince Charles, or an earl of several Mansfields. David Attenborough talking through a mouthful of grapes.

‘Was it a comet? Was it a supernova?’ The narrator was onto the mystery of the Star of Bethlehem. ‘Was it a conjunction of “wandering stars” that we now know as planets?’

He explored each possibility as we watched it take shape above us. A bright star recorded in Capricorn by the Chinese in the spring of 5 BC. Planetary alignments in Pisces in 5 and 6 BC, with the fish later to become a secret Christian sign. Several others, but with no more certainty at the end of the show than at the start.

Michael watched it all with his head craned back and his mouth open, his hand sweating on mine.

Part two was ‘Voyage to the Giants’. It began with a burst of classical music – duh-nu-nu-nuuuuh duh-nu-nu-nuuuuh.