aware of the construction of Chain Home but were not sure of its purpose. They tested their theories with a flight of the Zeppelin LZ 130 but concluded the stations were a new long-range naval communications system. As early as 1936, it was realized that the Luftwaffe would turn to night bombing if the day campaign did not go well. Watson-Watt had put another of the staff from the Radio Research Station, Edward Bowen, in charge of developing a radar that could be carried by a fighter. Night-time visual detection of a bomber was good to about 300 m and the existing Chain Home systems simply did not have the accuracy needed to get the fighters that close. Bowen decided that an airborne radar should not exceed 90 kg (200 lb) in weight or 8 ft³ (230 L) in volume, and should require no more than 500 watts of power. To reduce the drag of the antennae, the operating wavelength could not be much greater than one metre, difficult for the day's electronics. However, Airborne Interception (AI), was perfected by 1940 and was instrumental in eventually ending The Blitz of 1941. Watson-Watt justified his choice of a non-optimal frequency for his radar, with his oft-quoted "cult of the imperfect", which he stated as "Give them the third-best to go on with; the second-best comes too late, [and] the best never comes". Civil Service trade union activities Between 1934 and 1936, Watson-Watt was president of the Institution of Professional Civil Servants, now a part of Prospect, the "union for professionals". The union speculates that at this time he was involved in campaigning for an improvement in pay for Air Ministry staff. Contribution to Second World War In his English History 1914–1945, the historian A. J. P. Taylor paid the highest of praise to Watson-Watt, Sir Henry Tizard and their associates who developed radar, crediting them with being fundamental to victory in the Second World War. In July 1938, Watson-Watt left Bawdsey Manor and took up the post of Director of Communications Development (DCD-RAE). In 1939, Sir George Lee took over the job of DCD and Watson-Watt became Scientific Advisor on Telecommunications (SAT) to the Ministry of Aircraft Production, travelling to the US in 1941 to advise them on the severe inadequacies of their air defence, illustrated by the Pearl Harbor attack. He was knighted by George VI in 1942 and received