The Phantom Death Ray: How a British Inventor Fooled the Military and Vanished with the Secret

In the wake of the First World War, the world was gripped by a mixture of technological optimism and deep-seated military paranoia. It was a time when the line between science fiction and plausible reality seemed to blur. Into this charged atmosphere stepped Harry Grindell Matthews, a British inventor with a claim so audacious it captured the imagination of the public and the cautious attention of the government: he had invented a “death ray.”

The Man Behind the Ray

Before his infamous claim, Harry Grindell Matthews was a respected, if somewhat eccentric, inventor. He had already made significant contributions to technology, including developing the “aerophone”—a pioneering radiotelephone—and creating the world's first 'talking picture' in 1921. His legitimate successes lent a crucial air of credibility to his next, more fantastical project. He wasn't just some crackpot; he was a man who had delivered on technological promises before.

A 'Diabolical' Demonstration

In 1923, Matthews unveiled his invention, which he claimed could project a beam of energy capable of stopping engines, detonating gunpowder, and even killing living creatures from a distance. He held a private demonstration for journalists, successfully using his ray to stop a motorcycle engine from 50 feet away. The press went wild, dubbing it the “diabolical ray.”

The British Air Ministry and Admiralty were intrigued enough to investigate. Matthews demonstrated his device for them, successfully igniting gunpowder from afar and reportedly killing a mouse (though accounts of this vary). However, when officials requested a demonstration under scientifically controlled conditions where they could inspect his equipment, the inventor balked. An Air Ministry official reported:

“The inventor was not prepared to give a demonstration under our conditions on the grounds that we might discover his secret.”

The Vanishing Act

This became Matthews’ signature move. After a tantalizing but incomplete demonstration, he would refuse to proceed, often citing fears of his secrets being stolen or claiming his honor had been impugned. He would then disappear, taking his mysterious black box with him. He once vanished from a demonstration for the Admiralty after an officer, Fuller, accused him of being a fraud. Matthews seized on the accusation as the perfect excuse to pack up and leave.

Despite the military’s deep skepticism—many officials believed he was an elaborate fraud—Matthews managed to extract thousands of pounds from investors and even the government, always promising a full reveal that never came. He would resurface in France or the United States, running the same play on a new, eager audience.

Unmasking the Trick

So what was really going on? The consensus among scientists at the time, and historians today, is that the “death ray” was a clever hoax. The observed effects were likely achieved not with a revolutionary beam, but with simple, well-hidden electrical tricks. Experts suggested Matthews was likely using a high-tension coil (a Tesla coil) to ionize the air, creating a conductive path to short out the motorcycle's magneto ignition system. The demonstrations were theatre, designed to impress the scientifically uninitiated and prey on the fears of an anxious age.

The Legacy of the Phantom Ray

Harry Grindell Matthews never produced a working death ray for any government. He continued his inventive career, working on sound for films and other less dramatic projects. But the story of his diabolical ray became his lasting legacy—a perfect cautionary tale about the power of hype, the allure of secret weapons, and the fine line between genius and grift. It remains one of history’s most fascinating scientific hoaxes, a testament to a man who successfully sold the world a ghost in a machine.

Sources

• Wikipedia: Harry Grindell Matthews
• BBC News: The Welshman who invented the 'death ray'
• Wired: May 27, 1924: ‘Death Ray’ Inventor Seeks Huge Payout