Sarah was on holiday in a limestone area, which had lots of crevices, gullies, hidden caverns and secret waterfalls. She thought that such a landscape must make the inhabitants prone to deviousness. With subterranean halls hidden beneath a seemingly bland surface, you’d naturally learn to expect the worst, and not to believe the evidence of your own eyes. Limestone people were watchful and sly.

It was a cold day, with the occasional bright shaft of sunlight. Rambling across the hills, Sarah lost the footpath. She took a wrong footing athwart a boulder, slipped and sat down with a bump. Then she saw it. There, behind a large gorse bush, was a slit in the rock.

It was rather tight, but she managed to slip through. The desire to explore was stronger than the fear of being lost. She knew she was taking a risk, having neither companions nor equipment, but she had a good torch and stout shoes. She walked underground for what seemed a considerable time, then the path widened out. It became a huge, high gallery.

She played her torch on the walls and almost staggered with surprise. They were covered with drawings. Of course, on the way in, she’d toyed with the idea that she might find neolithic cave paintings like those in France - bison, deer. She knew that those paintings had been interpreted as spells or votive offerings, and that they bodied forth the inner lives of the people then - hunter and hunted, sacred hands and spears. But these paintings were nothing like that. Nothing.

From floor to ceiling, the walls were covered with images of plenitude - burgeoning, bustling, full-to-bursting. They portrayed the most astonishing double figures. Male twined about female, male about male, female about female. But it did not stop there. There were figures that were half-man, half-horse: others that were half-woman, half-tiger. And there were animal ones too: half-monkey and half-cat, half-elephant and half-rhino. And there were mixtures of animal and plants: a woman growing out of a rose, a man with a lily growing out of his generative parts. There was even a woman giving birth to a daisy-chain, and laughing as she did so. There was a man ejaculating a whole cluster of stars.

These paintings would change everything. Whenever this dreamtime was, there was clearly no desire in it for hierarchy or control. Once, in this place, emptiness and difference did not exist. Sarah knew she must tell everybody. But first of all, she had to get out, and that was easier said than done.

She tried retracing her steps, but soon lost her way. If only she’d had the wit to leave a thread or some crumbs! She went back to the gallery and thought she saw a tiny speck of light aloft. With the torch battery fading, climbing upwards was her only option. And so she clambered, scraped, and pushed until she tumbled out onto the grassland above. It was dusk. Sarah ran to her car and told the people at the hotel about her find. They seemed dubious and nonplussed. But they agreed to come with her next day to find the treasure. In the morning, armed with lights, ladders and ropes, they strode with her over the grassland.

But the slit in the rock could not be found. They went over the ground with a toothcomb, but there was no sign of the path Sarah had taken or the painted gallery she had found. Those images would have revolutionised historians’ views about the mental landscapes of the denizens of the far past. But they were lost again, perhaps for good this time. Perhaps all that had happened was that a silly woman had imagined pictures of a sensuous, teeming earthly playground, and a world without strict boundaries. That must have been it.