Table Mountain had been burning for two days. The fire had started at Bakoven, on the Camps Bay side, crossed over Devil’s Peak, and on a clear day in April or May 1969 it was working down towards Newlands Forest and Kirstenbosch. Stewart Bloch, a Waldorf School pupil who had joined the regional bush fire service as a volunteer with two classmates, climbed Newlands Ravine above Rhodes Memorial, past the contour path, and planted himself on rocky scree in the middle of the ravine, where nothing grew and, he reasoned, nothing could burn.

Five minutes in, something glinted at the edge of his left eye, slow and rhythmic. He took it for a firefighter over on the Kirstenbosch side flashing a mirror. It was not. Close against the rock face of Window Pane Gorge was an object turning over once every two seconds, and it was coming his way. It took, he said, about seven minutes to arrive.

What arrived was shaped, in his word, like a transformer: a mirrored outer frame the colour of magnesium foil, about four and a half metres wide, flipping over and over around a static central barrel the colour of pyrite, skinned, he said, in five millimetres of laminated polycarbonate. No rivets, no ports, no seams except slip joints at the barrel ends. It kept a constant height whatever the slope did beneath it, and it made no loud noise.

Not loud, but not silent either. At five metres he heard a rising whine, “wheeet, wheeet”, climbing in pitch and volume with each half flip of the frame. The barrel crackled. Then the air thickened until he found it hard to breathe, and every other sound, the fire, the city traffic below, the panicking birds, cut out. The hair on his body pressed flat. It passed a metre over his head with no heat and hardly any wind. He decided to hit it with a stick to find out whether it was hollow. A voice in his head told him not to: the energy governing the craft, it said, would run down the wood and hurt or kill him.

It circled him, out of reach. Wherever it passed low over burning ground, he said, the flames went out beneath it and relit once it had gone. After a third pass it settled over a level patch ten metres upslope, stopped turning, and sank. Triangular points of iridescent blue light came up in the four corners of the frame, brightened to white, and the vegetation under each turned bright red without burning. Half a metre up it stopped, on nothing, and hung there. He walked to within two metres. Then the fire arrived, burned under and around it, and never touched it: a gap of about forty millimetres, he said, between flame and surface, and no blackening.

Smoke drove him down the mountain before it left. He told two schoolmates, Francis Molteno and Paul Bartels, and nobody else for a long time. Told to Pam Puxley, the story reached Cynthia Hind, who printed it in July 1995 with a comment more puzzled than sceptical. How, she asked, could he name pyrite and five millimetres of laminated polycarbonate with such conviction? She let it stand, because Puxley was trusted, and because a report so precise would, she felt, be wrong to dismiss.

Bloch had run his own experiment. He had lain naked in a warm bath, he wrote in a footnote, with two powerful magnets under the water, and forced their like poles together. In his head, he reported, he heard the whine.