Question: 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?

full_context: Document 1: Tupolev Tu-104: The Tupolev Tu-104 (NATO reporting name: Camel) was a twin-engined medium-range narrow-body turbojet-powered Soviet airliner and the world's first successful jet airliner. Although it was the sixth jet airliner to fly (following, in order, the British Vickers Type 618 Nene-Viking, de Havilland Comet, Canadian Avro Canada C102 Jetliner, US Boeing 367-80 and French Sud Caravelle), the Tu-104 was the second to enter regular service (with Aeroflot) and the first to provide a sustained and successful service (the Comet which had entered service in 1952, was withdrawn from 1954-1958 following a series of crashes due to structural failure). The Tu-104 was the sole jetliner operating in the world between 1956 and 1958.
Document 2: Airco: The Aircraft Manufacturing Company Limited (Airco) was a British aircraft manufacturer operating from 1912 to 1920. Airco produced thousands of aircraft for the British military during the First World War, most of which were designed by their chief designer, Geoffrey de Havilland. Advertised in 1918 as the largest aircraft company in the world, Airco established the first airline in the United Kingdom, Aircraft Transport and Travel Limited, as a subsidiary. A glut of war surplus aircraft and a lack of government interest in aviation caused the company to become unprofitable, and in 1920 it was sold to Birmingham Small Arms Company, who had its operations liquidated later that year.
Document 3: Geoffrey de Havilland: Captain Sir Geoffrey de Havilland (27 July 1882 – 21 May 1965) was a British aviation pioneer and aircraft engineer. His Mosquito has been considered the most versatile warplane ever built, and his Comet was the first jet airliner to go into production.
Document 4: Avro Canada C102 Jetliner: The Avro C102 Jetliner was a Canadian prototype medium-range turbojet-powered jet airliner built by Avro Canada in 1949. It was beaten to the air by only 13 days by the de Havilland Comet, thereby becoming the second jet airliner in the world. The name "Jetliner" was chosen as a shortening of the term "jet airliner", a term which is still in popular usage in Canada and the United States. The aircraft was considered suitable for busy routes along the US eastern seaboard and garnered intense interest, notably from Howard Hughes who even offered to start production under license. However continued delays in Avro's all-weather interceptor project, the Avro CF-100, led to an order to stop working on the project in 1951, with the prototype Jetliner later cut up for scrap.
Document 5: Hawker Hunter: The Hawker Hunter is a transonic British jet-powered fighter aircraft that was developed by Hawker Aircraft for the Royal Air Force (RAF) during the late 1940s and early 1950s. It was designed to take advantage of the newly developed Rolls-Royce Avon turbojet engine and the swept wing, and was the first jet-powered aircraft produced by Hawker to be procured by the RAF. On 7 September 1953, the modified first prototype broke the world air speed record for aircraft, achieving a speed of 727.63 mph .
Document 6: De Havilland Sea Vixen: The de Havilland DH.110 Sea Vixen is a twin boom, twin-engined 1950s–60s British two-seat jet fighter operated by the Fleet Air Arm. It was designed by de Havilland during the late 1940s at its facility in Hatfield, Hertfordshire. Developed from an earlier first generation jet fighter, the Sea Vixen was a carrier-based fleet defence fighter that served into the 1970s. Initially produced by de Havilland, it was later known as the Hawker Siddeley Sea Vixen after de Havilland became a part of the Hawker Siddeley group in 1960.
Document 7: De Havilland Mosquito: The de Havilland DH.98 Mosquito was a British twin-engine shoulder-winged multi-role combat aircraft. The crew of two, pilot and navigator, sat side by side. It served during and after the Second World War. It was one of few operational front-line aircraft of the era constructed almost entirely of wood and was nicknamed "The Wooden Wonder". The Mosquito was also known affectionately as the "Mossie" to its crews. Originally conceived as an unarmed fast bomber, the Mosquito was adapted to roles including low to medium-altitude daytime tactical bomber, high-altitude night bomber, pathfinder, day or night fighter, fighter-bomber, intruder, maritime strike aircraft, and fast photo-reconnaissance aircraft. It was also used by the British Overseas Airways Corporation (BOAC) as a fast transport to carry small high-value cargoes to, and from, neutral countries, through enemy-controlled airspace. A single passenger could ride in the aircraft's bomb bay when it was adapted for the purpose.
Document 8: Hunting-Clan Air Transport: Hunting-Clan Air Transport was a wholly private, British independent airline that was founded in the immediate post-World War II period. It began trading on January 1, 1946 as Hunting Air Travel Ltd. It was a subsidiary of the Hunting Group of companies, which had come from the shipping industry and could trace its history back to the 19th century. The newly formed airline's first operating base was at Bovingdon Airport in Southeast England. Its main activities were contract, scheduled and non-scheduled domestic and international air services that were initially operated with Douglas Dakota and Vickers Viking piston airliners from the company's Bovingdon base. A change of name to Hunting Air Transport occurred in 1951. By that time, the airline had emerged as one of the healthiest and most securely financed independent airlines in Britain. In October 1953, the firm's name changed to Hunting-Clan Air Transport, as a result of an agreement between the Hunting Group and the Clan Line group of companies to invest £500,000 each in a new company named Hunting-Clan Air Holdings Ltd, the holding company for the combined group's air transport interests. Apart from Hunting-Clan Air Transport itself, this included Field Aircraft Services Ltd, the Hunting group's aircraft maintenance arm. In 1960, Hunting-Clan Air Transport merged with the Airwork group to form British United Airways (BUA).
Document 9: Bede Aircraft: Bede Aircraft Corporation was founded by controversial aeronautical engineer Jim Bede in 1961 to produce the BD-1 kit aircraft, which eventually became the American Aviation Corporation's AA-1. The company also created and produced a number of advanced kit planes including the famous Bede BD-5 (pusher propeller driven) and BD-5J (turbojet driven). The BD-5J has held the Guinness record as the World's Smallest Jet Aircraft for more than a quarter century. Versions of it saw use in various Budweiser commercials (the Bud Light Jet, which was lost in an inflight fire and crash unrelated to airshow work). The tiny jet also appeared in two James Bond movies; "Octopussy" starring Sir Roger Moore, and later in a cameo appearance, hanging from the wall of Q's workshop in "Die Another Day" starring Pierce Brosnan as Agent 007.
Document 10: De Havilland DH.37: The de Havilland DH.37 was a British three-seat sporting biplane of the 1920s designed and built by de Havilland for Alan Samuel Butler. The first —named Sylvia after Butler's sister— of the two examples built flew extensively for five years before being converted to a single-seater and having its engine upgraded to a 300 hp (224 kW) A.D.C. Nimbus . It crashed in June 1927.
Document 11: Alan Samuel Butler: Alan Butler (22 November 1898 —24 May 1987), full name Alan Samuel Butler, was (claimed his obituary in "The Times") the first private aeroplane owner-driver. 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.
Document 12: Boeing 747: The Boeing 747 is an American wide-body commercial jet airliner and cargo aircraft, often referred to by its original nickname, ""Jumbo Jet"". Its distinctive "hump" upper deck along the forward part of the aircraft makes it among the world's most recognizable aircraft, and it was the first wide-body produced. Manufactured by Boeing's Commercial Airplane unit in the United States, the original version of the 747 was envisioned to have 150 percent greater capacity than the Boeing 707, one of the common large commercial aircraft of the 1960s. First flown commercially in 1970, the 747 held the passenger capacity record for 37 years.
Document 13: Claud Butler: Claud Butler (14 July 1903 – 2 November 1978) was a London-based bicycle dealer and frame-builder, who from 1928 created a chain of bicycle-retail shops in London and the Midlands. His company was one of the most successful of the inter-war era but failed after World War II and the resultant boom in motor buses and motor cars. The Claud Butler brand was bought from the receivers by other companies, and they are now produced by Falcon Cycles, a division of Tandem Group.
Document 14: De Havilland Comet: The de Havilland DH 106 Comet was the world's first commercial jetliner. Developed and manufactured by de Havilland at its Hatfield Aerodrome, Hertfordshire, United Kingdom headquarters, the Comet 1 prototype first flew on 27 July 1949. It featured an aerodynamically clean design with four de Havilland Ghost turbojet engines buried in the wings, a pressurised fuselage, and large square windows. For the era, it offered a relatively quiet, comfortable passenger cabin and showed signs of being a commercial success at its 1952 debut.
Document 15: De Havilland DH 108: The de Havilland DH 108 "Swallow" was a British experimental aircraft designed by John Carver Meadows Frost in October 1945. The DH 108 featured a tailless, swept wing with a single vertical stabilizer, similar to the layout of the wartime German Messerschmitt Me 163 "Komet" rocket-powered point-defence interceptor. Initially designed to evaluate swept wing handling characteristics at low and high subsonic speeds for the proposed early tailless design of the Comet airliner, three examples of the DH 108 were built to Air Ministry specifications E.1/45 and E.11/45. With the adoption of a conventional tail for the Comet, the aircraft were used instead to investigate swept wing handling up to supersonic speeds. All three prototypes were lost in fatal crashes.
ground_truth: Hertfordshire