Robert Watson-Watt(1892–1973)

Robert Alexander Watson Watt was born at 5 Union Street in Brechin, Angus, on the thirteenth of April 1892, the youngest of four sons of Patrick Watson Watt, a master cabinetmaker, and Mary Small Matthew. The family carried, by careful genealogical tradition, descent in the direct male line from James Watt the eighteenth-century engineer; Watson Watt would in 1942, on being knighted, hyphenate his surname into Watson-Watt and from then on use it in that form. He took his first degree at University College, Dundee, then part of the University of St Andrews, graduating with a BSc in engineering in 1912. He stayed on as an assistant to the professor of natural philosophy, William Peddie, the man who first turned his attention to the properties of radio waves.

In 1915 he joined the Meteorological Office as a meteorologist working on the use of radio for the detection and location of thunderstorms, by direction-finding on the radio bursts called atmospherics that lightning discharges generate. He spent the whole of the First World War and most of the interwar period on this work, first at Aldershot and then at Slough, and built up over twenty years one of the deepest practical understandings in the world of how radio waves are emitted, propagated, reflected and located in the atmosphere.

In January 1935 the Air Ministry's new Committee for the Scientific Survey of Air Defence, chaired by Henry Tizard, asked Watson Watt whether a death-ray weapon could be built that would knock down enemy aircraft by directed radio energy. He gave the question to his young assistant Arnold Wilkins, who calculated in a back-of-an-envelope estimate that the powers required were impossibly large; but, Wilkins added, the same energies were trivial for the inverse problem, the location of an aircraft by the radio waves reflected from its airframe. Watson Watt wrote up the answer in a memorandum dated the twelfth of February 1935, titled Detection and Location of Aircraft by Radio Methods, and sent it to the Committee.

On the twenty-sixth of February 1935, in a field at Stowe Nine Churches near Daventry, Watson Watt and Wilkins set up a receiver in the back of a Morris Commercial van and persuaded a Handley Page Heyford bomber of the Royal Air Force to fly back and forth across the beam of the BBC Empire Service shortwave transmitter at Borough Hill. The reflected signal from the aircraft was clearly detectable on the cathode-ray tube of the receiver out to a range of about eight miles. It was the first demonstration of the radio detection of aircraft in any country. The Air Ministry funded the work without further delay; Watson Watt was made superintendent of the new Bawdsey Research Station on the Suffolk coast in 1936 with a team and a budget, and over the next three years built the Chain Home network, the ring of twenty high-powered radar stations along the south and east coasts of Britain that came into full operational service in the spring of 1939.

When the Battle of Britain opened in July 1940, the small fighter force of the Royal Air Force was for the first time in the history of air warfare directed onto its targets by a national early-warning system that gave it accurate range, bearing and height of incoming raids while they were still over the French coast. The historians of the battle have agreed since that Chain Home, more than any other single technical advantage, was what made the defence possible. Watson-Watt was knighted in 1942, served as scientific adviser to the Ministry of Aircraft Production through the rest of the war, received the United States Medal for Merit in 1946, and was elected to the Royal Society in the same year. He died at Inverness on the fifth of December 1973 and is buried in the churchyard at Pitlochry. The Watson name in modern engineering carries the weight of the day at Daventry on which a Brechin engineer first saw an aeroplane on a screen by the radio echo from its wings.