On 4 August 1914 Britain went to war with Germany, and the Union of South Africa went with her. A week later, on the night of 11 August, somebody saw an aeroplane. Then somebody else did. By the end of the month it was everywhere.

The Cape Times had it over the Peninsula: a mysterious flight seen from Sea Point, later the aeroplane on Table Mountain. The Rand Daily Mail had it at Vryburg, under the headline Aerial Scouts, a German aeroplane near the Bechuanaland line. The Cape Argus found it at Porterville and at Ashton, and then, a few days later, at Hoetjes Bay near Saldanha. The Natal Advertiser had reports from the Natal countryside and then more reports from Natal. The Pretoria News had it at Warmbaths and at Skinner’s Court. Nearly forty separate newspaper items between the middle of August and the second week of September, in six papers, from the Atlantic to the Indian Ocean.

What people described was strikingly consistent and strikingly odd. A single bright light, usually low over the horizon at dusk or before dawn, which they took to be the headlight of a monoplane. Some said it climbed, dipped and circled with a nimbleness no pilot of 1914 could have managed. Some heard an engine. Nobody saw it land, nobody saw where it took off, and nobody found a pilot, a petrol dump or a tyre track.

The explanation everybody reached for was Germany. South West Africa was a German colony next door, the Union was about to invade it, and a spy plane over the Cape made a kind of sense. It made less sense to anyone who knew about aeroplanes. The Cape Times asked the Defence Department, which admitted the Union owned no machines at all. It asked John Weston, the country’s aviation pioneer, who was polite about the air visitors. Its own reporter counted the aeroplanes in German South West: there were three, one of them serviceable, none with the range to reach Cape Town and get home, or to stay up for the hours the witnesses described. The nearest German airfield was as far from Sea Point as London is from Warsaw.

By early September the papers had turned. Aeroplane or planet, asked the Cape Argus. A Pietermaritzburg optician offered his solution to the aeroplane problem, and the Rand Daily Mail described a coloured planet. A bright planet seen low through moving air twinkles, changes colour and appears to dart, and a country that had just gone to war was ready to see it move.

The American sociologist Robert Bartholomew wrote the episode up in 1989 as a textbook case of a hysterical belief: thousands of people, over four weeks, misperceiving the same ordinary lights because a war had told them what to expect. It sits in the histories beside the British scareship panics of 1909 and 1913 and the New Zealand airship of 1909, all of which happened in the years when aeroplanes were new enough to be magical and old enough to be feared.

The sightings stopped on about 9 September. The invasion of German South West Africa went ahead that month, and the Union’s soldiers found the three German aeroplanes exactly where they were supposed to be.