Robert Watson-Watt

The radio engineer who proved in 1935 that an aircraft could be detected by a reflected radio wave, and who built the Chain Home early warning system. Robert Alexander Watson-Watt was born on 13 April 1892 at Brechin in Scotland. He worked at the Radio Research Station on the direction-finding of thunderstorms — the problem out of which everything else grew, since it taught him to locate the source of a radio wave from the timing and bearing of its arrival. On 12 February 1935 he sent the Air Ministry a secret memorandum, "Detection and location of aircraft by radio methods". By 26 February the experiment was ready. Two receiving aerials were set up about six miles from the BBC shortwave transmitter at Daventry and phased so that the direct signal cancelled while reflections came through. A Handley Page Heyford bomber, flown around the site, produced clear returns. Radar stopped being a hypothesis. Out of this came Chain Home, the line of fixed radar towers along England's east and south coasts, in service from 1938; nineteen stations were working by the outbreak of war. Its value was not only technical: it bought time. In the Battle of Britain fighters were not sent up on speculative patrols but onto a known course, and a small air force could be spent where it was needed. He was elected a Fellow of the Royal Society in 1941 and knighted in 1942. Ten years after that the government paid him £50,000 for his radar work. He received the American Medal for Merit in 1946 and the Hughes Medal in 1948. In 1956, in Canada, he was stopped by a policeman with a radar speed gun. Had he known what they would do with it, he remarked, he would never have invented it. He died at Inverness on 5 December 1973.