How long is it really — two seconds, three? I'd heard the number so often I stopped believing it, so I went and looked. It's a handful of frames. A garden at Oakwood Grange in Roundhay, Leeds, autumn light, grass that clearly got cut for the occasion. Four people walking in a loop because someone has told them to keep moving: Le Prince's son Adolphe, his wife's parents Joseph and Sarah Whitley, and a family friend, Harriet Hartley. One of them turns and goes backwards for a step or two, the way you do when you've been asked to circle and run out of circle. A skirt swings. That's the whole of it, 1888.

Cut to the thing I keep forgetting: there was no screen. No house lights, no fourth row, no curtain going up on a ribbon of celluloid. The first audience was whoever stood behind the camera in that garden and watched four people walk — and then, later, whoever Le Prince let look at the strip. He filed the British patent for the camera about a month after. So the oldest surviving film had an audience of roughly one, outdoors, in a coat.

Sarah Whitley died ten days later. She's the one who goes round at a good clip, skirts out, not performing anything. Her son-in-law was testing a machine and she turned up on the lawn to help him do it, and that's why there's a few seconds of her left at all.