It was while he was studying X-rays at the University of Nancy that Blondlot stumbled across a strange phenomenon. Working with a platinum filament inside a metal tube, he noticed that radiation leaking from the apparatus seemed to increase the luminosity of a gas flame. On further investigation, he found that this new form of radiation - he chose the “N” label in honour of Nancy - caused a screen coated with calcium sulphide to glow.

Soon, Blondlot was detecting N-rays everywhere. For, with the exception of green wood and certain treated metals, they seemed to come from everything in nature, especially wrapped bricks. With an ability to intensify flames and sparks, they offered the prospect of enhanced vision in dim lighting.

The only drawback was that loud noises caused them to dissipate. Blondlot wasn’t the only scientist to observe N-rays. Dozens replicated his experiments, among them Jean Becquerel.

But acceptance was not universal. Having published his original paper, the magazine Nature arranged for the US physicist Robert W Wood to visit Blondlot. At which point, science gave way to French farce. In the darkened lab, Wood surreptitiously removed a crucial prism from the apparatus. But in spite of this, Blondlot’s assistant still “saw” the N-rays. Before the next demonstration, Wood replaced the prism, but was spotted by the assistant, who assumed he was removing it. Accordingly, the N-rays then failed to appear, even though the apparatus was actually intact.

Although Wood’s report was enough to destroy Blondlot, N-rays did not go down in history as a hoax. The episode is regarded as a classic illustration of how researchers can see what they want to see. And Blondlot continued to “see” N-rays until his death in 1930. But by then, the world was no longer listening.