But we were all water babies. Alice was shrieking at the green slime that Henry flicked with a stick from the stream. I showed them a dead water beetle, but they were more interested in an aerosol paint can that floated between the reeds. It still held some of its propellent gas, and Henry fired a burst of spray at a dragonfly that veered too close.

Trying to repaint the air, we moved through the willows to the water splash that crossed the road. The water ran clear over the worn pebbles, but cars taking a shortcut to Shepperton often stalled there. The exasperated drivers would look up to find a beaming audience of mothers and their children curious to see what they would do next. It was here that the water-splash sequence from Genevieve had been filmed. Whenever Miriam and I watched the scene of the stranded antique car we could see ourselves, Henry, and Alice out of shot as we leaned on the polished rail of the footbridge.

Led by the retriever, we set off along the upper arm of the stream, collecting more children on our way. The rectangular stages of Shepperton film studios rose above the trees. Their presence dominated the town as much as the marine world of the reservoirs. Many of the programmes we watched on television were filmed in the streets of Shepperton, and its leafy avenues stood in for locations all over England. In Henry’s intense four-year-old mind, Shepperton had begun to colonise the whole country.

These confusions of image and illusion gave Shepperton its special charge, as if true reality rested in the merging of the two. Next door to us lived a married couple whose daughter was a minor television actress. Twice a week the children watched her appear in one of their favourite series, and sometimes would turn from the screen to see her in Charlton Road, stepping from her car on a family visit. Henry and Alice would rush out to greet her, taking for granted that her real character lay somewhere between her fleeting street-self and the far more solid broadcast figure on the screen. Many of our neighbours worked as extras in feature films made at Shepperton studios, and I sometimes felt that Miriam and I were playing our parts in some happily chaotic sitcom whose script we extemporised as we went along.

The children squatted on the edge of the gravel lake and stared at a submerged motorcar resting on the sandy bed. The lake had been stocked by a local fishing club, and rainbow trout swam through the open windows. These drowned cars never failed to intrigue Alice and Henry.

“Henry, where’s the car going?” Alice asked.

“Going a long way,” he told her. “Going to China.”