Quarter past eleven at the top of the pass, and nothing on the road. The moon was up, but the peak threw most of the plateau into shadow. In a small second-hand French car sat an instrumentation engineer from Paarl whom Cynthia Hind called Henry (his real name stayed in her files). He had spent the evening servicing his wife’s car and driven up to charge its flat battery. He was about to head home, he said, when a man stepped out of the dark with an arm raised.

He came to the window and asked for water. Only in the radiator, said Henry. “We are badly in need of water,” the man said, in an accent Henry could not place, which in South Africa takes some doing. There was a spring half a kilometre on. They scoured an oil can from the boot with sand, filled it and drove back, and the man pointed into the blackness under the peak.

Once his eyes adjusted, Henry said, he made out something about a hundred metres off the road: circular, ten to fifteen metres across, four metres from legs to top, with a lit opening underneath and a ladder. He climbed it reluctantly, at the man’s polite insistence.

Inside was a round room with windows all the way round, a bench beneath them, and four more men, one lying down: burned, his guide explained, when a window cracked on entering the atmosphere, and no, they did not need a doctor. The crew were slight, perhaps a metre and a half tall, in belted cream smocks. Two rows of levers like those in a railway signal box rose from the floor, and behind them a console with no dials, panels or navigation gear, which, as an instrument engineer, he found curious. Light came from everywhere and from nothing.

He asked where the engines were. There were none, he was told: the levers annulled gravity, a very heavy fluid circulated in a tube, and the craft rose at forty-five degrees, never straight up. Asked where they came from, the man pointed through a window at the stars, said “From there,” and nothing more. After fifteen or twenty minutes Henry was steered back to the ladder and drove home.

His wife told him he had been dreaming. His colleagues were interested for two hours, until the general manager sent for him and said that if he did not stop talking rubbish he would be fired. He stopped. Next afternoon he went back and found, on rough ground, what he took to be two dinner-plate impressions, diagonally opposite; or, he allowed, his imagination. The oil can was gone from the car.

The story stayed put until the Spanish investigator J J Benitez heard it in 1977. It reached Hind from Spain, and in February 1989 she drove up the pass. The plateau, thirteen kilometres from his old farm, the 820 metre sign and the stream under its culvert were there; his firm, and any farm in his name, were not. Over lunch in a Portsmouth pub in 1991 he conceded the car had needed four or five turns to come round, said he would tell no one if he had his time again, and was never sure of the year: summer 1951 in one telling, Christmas 1952 in another.

Henry died in Spain late in 1996. As for the oil can, the one thing that convinced him it was no dream: the farm labourers, he admitted later, loved those cans for keeping water in their huts, and it could quite likely have been stolen.