The talk in the local paper was of shotgun-wielding hoodlums, and when the same thing started happening 25 miles away, the police swung into action with a dawn swoop and a string of roadblocks.

When the problem spread to a nearby naval base, 75 marines conducted a five-hour search of the area. But at the end of the day, only one thing was certain - with more than 2,000 cars damaged, this was more than vandalism.

By now, the Seattle papers had got hold of the story, and with the city clearly in the path of the epidemic, a siege mentality took hold. When the first reports came in of pitted windscreens, near panic broke out. Drivers flagged down police cars in the street and extra staff were called in to answer the flood of calls.

According to sheriff Tom Clark, a likely cause was radiation released by H-bomb tests in the Pacific. However, if he was right, nothing was showing up on the Geiger counters. Perhaps the powerful naval transmitter at Arlington was the problem, or cosmic rays, or supersonic vibrations.

Someone suggested radioactive coral from the bomb tests, and even sand fleas were blamed.

When a desperate mayor of Seattle wired President Dwight Eisenhower for assistance, a committee of scientists was set up to investigate, and that’s when it was noticed that older cars seemed to have been targeted, while newer models were apparently escaping undamaged. The explanation, the scientists concluded, was quite simple - the pockmarks had been there all along, having been caused by normal wear and tear. Only when motorists were alerted to their presence by rumours and stories in the press did they begin looking at their windscreens rather than through them. The whole phenomenon, in fact, was nothing more than a case of collective delusion.

David Newnham