The theory of radio transmission, or 'telegraphy without wires', was first put forward by British physicist James Clerk Maxwell. In 1864 he argued mathematically that radio waves behaved as light does, and travelled at the speed of light. In 1888 Heinrich Hertz in Germany created electromagnetic waves experimentally and demonstrated that Maxwell's theory was correct. Other scientists, among them David Hughes, Oliver Lodge and Nikola Tesla, carried out further research, but it was a young Italian, Guglielmo Marconi, who realised the potential of radio for communicating. Although not himself a great innovator, he made use of the best available ideas and turned them into a commercially viable system of communication. By December 1903 he had demonstrated that radio waves could span the Atlantic.
The early radio systems could only be used for morse or similar code, so for 20 years or so the airwaves were monopolised by governments and commercial organisations sending and receiving messages. Speech or music broadcasts needed electronic detection and amplification, made possible by the development of thermionic valves by J. A. Fleming in Britain in 1904. An American, Lee de Forest, produced a modification in 1907 that turned these valves, or 'tubes', into devices capable of amplification.
The introduction of valve technology was slow, but by about 1920 it was ready to be exploited on a wider scale. The radio equipment manufacturers realised that there was potentially a huge new market for the sale of radio receivers if entertainment programmes were allowed to be broadcast. In the United States there was no government restriction on use of the airwaves and hundreds of radio stations soon sprang up.
In Britain, government control was absolute. The Marconi Company was permitted only one experimental evening of broadcasting a week, but public response and pressure from industry led to further trials. In 1922 a consortium of manufacturers set up the British Broadcasting Company (BBC). Its first broadcast came from the ex-Marconi station 2LO in London on 14 November 1922; other British towns and cities soon followed.
At first valve receivers with loudspeakers were too expensive for most people, so they 'listened in' on cheaply made crystal sets using headphones. The price of valve radio sets soon started to drop, and within a decade 'listening to the wireless' in the living room at home was a familiar experience for millions. People in Britain could hear dance music, talks, plays, comedy or classical concerts every day.
The power of radio as a means of mass communication was demonstrated in 1926 when the BBC continued its own independent news transmissions against government opposition during the National Strike.
When the prime minister used radio to announce the outbreak of the Second World War in 1939, he was speaking to virtually the whole population of Britain. In less than 20 years a technical innovation that had been familiar to only a few became an essential component of mass communication.