In which county are the headquarters of this company located that developed one of the world's first commercial jet airliners built by Alan Samuel Butler?
Alan Samuel Butler:  From 1923 Butler was chairman of De Havilland Aircraft Company —which he financed— until 1950, a year when De Havilland employed 20,000 people and was building Comet, the world's first commercial jet airliner. De Havilland Comet:  Developed and manufactured by de Havilland at its Hatfield Aerodrome, Hertfordshire, United Kingdom headquarters, the Comet 1 prototype first flew on 27 July 1949.
i don't know