Death ray, fiddlesticks! Why, it doesn't even slow them up!

Wiki:

Harry Grindell Matthews (March 17, 1880 – September 11, 1941) was an English inventor who claimed to have invented a death ray in the 1920s.

Harry Grindell Matthews was born in 1880 in Winterbourne, Gloucestershire. He studied at the Merchant Venturer's School in Bristol and became an electronic engineer. During the Second Boer War he served in the South African Constabulary and was twice wounded.

In 1911 Matthews said he had invented an Aerophone device, a radiotelephone, and transmitted messages between a ground station and an aeroplane from a distance of two miles. His experiments attracted government attention and in July 4, 1912 he visited Buckingham Palace. However, when the British Admiralty requested a demonstration of the Aerophone, Matthews demanded that no experts be present at the scene. When four of the observers dismantled part of the apparatus before the demonstration began and took notes, Matthews canceled the demonstration and drove observers away.

Newspapers rushed to Matthews's defense. The War Office denied any tampering and claimed that the demonstration was a failure. Matthews backpedalled and stated that the affair was just a misunderstanding.

In 1914, after the outbreak of the First World War, the British government announced an award of £25,000 to anyone who could create a weapon against zeppelins or remotely control unmanned vehicles. Matthews claimed that he had created a remote control system that used selenium cells. He successfully demonstrated it with a remotely controlled boat to representatives of the Admiralty at Richmond Park's Penn Pond. He received his £25,000 but the admiralty never used the invention.

Next, Matthews appeared in public in 1921 and claimed to have invented the world's first talking picture, an interview of Ernest Shackleton. It was not commercially successful. (Other talking-picture processes had been developed before that of Matthews, notably one by William K.L. Dickson: these also were not successful, but they are thoroughly documented. Even if Matthews's process actually worked, it was certainly not the "first".)

In 1923 Matthews claimed that he had invented an electric ray that would put magnetos out of action. In a demonstration to some select journalist he stopped a motorcycle engine from a distance. He also claimed that with enough power he could shoot down aeroplanes, explode gunpowder, stop ships and incapacitate infantry from the distance of four miles. Newspapers obliged by publishing sensational accounts of his invention.

The War Office contacted Matthews in February 1924 to request a demonstration of his ray. Matthews did not answer to them but spoke to journalists and demonstrated the ray to a Star reporter by igniting gunpowder from a distance. He still refused to say how the ray actually worked, just insisted that it did. When the British government still refused to rush to buy his ideas, he announced that he had an offer from France.

The Air Ministry was wary, partially because of previous bad experiences with would-be inventors. Matthews was invited back to London to demonstrate his ray on April 26 to the armed forces. In Matthews's laboratory they saw how his ray switched on a light bulb and cut off a motor. He failed to convince the officials, who also suspected trickery or a confidence game. When the admiralty requested further demonstration, Matthews refused to give it.

In May 27, 1924, the High Court in London granted an injunction to Matthew's investors that forbade him from selling the rights to the death ray. When Major Wimperis arrived at Matthews's laboratory to negotiate a new deal, Matthews had already flown to Paris. Matthews's backers appeared on the scene as well and then rushed to Croydon airport to stop him, but were too late.

Public furor attracted interest of various other would-be inventors who wanted to demonstrate their own death rays to the War Office. None of them was convincing. On May 28 Commander Kenworthy asked in the House of Commons what the government intended to do to stop Matthews from selling the ray to a foreign power. The Undersecretary for Air answered that Matthews was not willing to let them investigate the ray to their satisfaction. A government representative also stated that one ministry official had stood before the ray and survived. Newspapers continued to root for Matthews.

The government required that Matthews would use the ray to stop a petrol motorcycle engine in the conditions that would satisfy the Air Ministry. He would receive £1000 and further consideration. From France, Matthews answered that he was not willing to give any proof of that kind and that he already had eight bids to choose from. He also claimed that he had lost sight in his left eye because of his experiments. His involvement with his French backer Eugene Royer aroused further suspicions in Britain.

Sir Samuel Instone and his brother Theodore offered Matthews a huge salary if he would keep the ray in Britain and demonstrate that it actually worked. Matthews refused again - he did not want to give any proof that the ray worked as he claimed it would.

Matthews returned to London June 1, 1924 and gave an interview to the Sunday Express. He claimed that he had a deal with Royer. The press again took his side. The only demonstration Matthews was willing to give was to make a Pathe film The Death Ray to propagate his ideas to his own satisfaction. The device in the movie bore no resemblance to the one government officials had seen.

In July 1924, Matthews left for the USA to market his invention. When he was offered $25,000 to demonstrate his beam to the Radio World Fair at Madison Square Garden, he again refused and claimed, without foundation, that he was not permitted to demonstrate it outside England. US scientists were not impressed. One Professor Woods offered to stand in front of the death ray device to demonstrate his disbelief. Regardless, when Matthews returned to Britain, he claimed that the USA had bought his ray but refused to say who had done it and for how much. Matthews moved to the USA and began to work for Warner Bros.