Robert Watson-Watt

Sir Robert Alexander Watson-Watt, (13 April 1892 – 5 December 1973) is considered by many to be the "inventor of radar". (The hyphenated name is used herein for consistency, although this was not adopted until he was knighted in 1942.) Development of radar, initially nameless, was first started elsewhere but greatly expanded on 1 September 1936 when Watson-Watt became Superintendent of a new establishment under the British Air Ministry, Bawdsey Research Station located in Bawdsey Manor, near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called Chain Home along the East and South coasts of England in time for the outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the Battle of Britain.

In 1934, the Air Ministry set up a committee chaired by Sir Henry Tizard to advance the state of the art of air defence in the UK. During World War I, the Germans had used Zeppelins as long-range bombers over London and other cities and defences had struggled to counter the threat. Since that time aircraft capabilities had improved considerably, and existing weapons were unlikely to have any effect on a raid.

Nazi Germany was rumored to have a "death-ray" using radio waves that was capable of destroying towns, cities and people. In January 1935, H.E. Wimperis, Director of Scientific Research at the Air Ministry, asked Watson-Watt about the possibly of building their version of a death-ray, specifically to be used against aircraft.^{[citation needed]} Watson-Watt quickly returned a calculation carried out by his assistant, Arnold Wilkins, showing that the device was impossible to construct, and fears of a Nazi version soon vanished. However he also mentioned in the same report: "Meanwhile attention is being turned to the still difficult, but less unpromising, problem of radio detection and numerical considerations on the method of detection by reflected radio waves will be submitted when required." 

On 12 February 1935, Watson-Watt sent a secret memo of the proposed system to the Air Ministry, entitled Detection and location of aircraft by radio methods. Although not as exciting as a death-ray, the concept clearly had potential but the Air Ministry, before giving funding, asked for a demonstration proving that radio waves could be reflected by an aircraft.This was ready by 26 February and consisted of two receiving antennas located about ten km away from one of the BBC's shortwave broadcast stations at Daventry. The two antennas were phased such that signals travelling directly from the station cancelled themselves out, but signals arriving from other angles were admitted, thereby deflecting the trace on a CRT indicator (passive radar).Such was the secrecy of this test that only three people witnessed it: Watson-Watt, his assistant Arnold Wilkins, and a single member of the committee, A.P. Rowe. The demonstration was a success; on several occasions a clear signal was seen from a Handley Page Heyford bomber being flown around the site. Most importantly, the prime minister, Stanley Baldwin, was kept quietly informed of radar's progress. On 2 April 1935, Watson-Watt received a patent on a radio device for detecting and locating an aircraft.