William A. S. Butement
William Alan Stewart Butement (☆ August 18, 1904 at Masterton, New Zealand – † January 25, 1990 at Richmond, Melbourne) was an British physicist and electrical engineer.
In 1915 the family moved to London. There he attended University College School (1917-22) and then studied at University College, University of London (Bachelor of Science, 1926). After two years as a research student in physics, in 1928 he joined the War Office’s signals experimental establishment at Woolwich as a scientific officer, where he helped to develop radio communication equipment for the British Army.
While in this role in 1939, Alan Butement devised a radar system which could detect and accurately position a ship at a much greater range than before; it could also detect and range low flying aircraft. The results of his experimental instalation were so positive that, in August 1939, the Air Ministry ordered a number of sets which became known as Chain Home Low (CHL) to complement the existing CH radar chain. The first CHL unit became operational in November 1939 and, by mid 1940, the CHL chain extended along the south and south-east coastline of Great Britain in time to play an important part in the Battle of Britain.