Question: In which city are the headquarters of the multinational defence, security and aerospace company, one of the world's largest and ranked 3rd based on revenues in 2015, which has the subsidiary British Aerospace? 
Context: BAE Systems plc is a British multinational defence, security, and aerospace company.  Its headquarters are in London in the United Kingdom and it has operations worldwide.  It is among the world's largest defence companies; it was ranked as the third-largest based on applicable 2015 revenues.  Its largest operations are in the United Kingdom and United States, where its BAE Systems Inc. subsidiary is one of the six largest suppliers to the US Department of Defense.  Other major markets include Australia, India and Saudi Arabia.  The company was formed on 30 November 1999 by the £7.7 billion merger of two British companies: Marconi Electronic Systems (MES) – the defence electronics and naval shipbuilding subsidiary of the General Electric Company plc (GEC) – and British Aerospace (BAe) – an aircraft, munitions and naval systems manufacturer. The Society of British Aerospace Companies, formerly Society of British Aircraft Constructors, known as SBAC, was the UK's national trade association representing companies supplying civil air transport, aerospace defence, homeland security and space.  As of October 2009 SBAC merged with the Defence Manufacturers Association and the Association of Police and Public Security Suppliers to form the ADS Group. ArianeGroup formerly Airbus Safran Launchers is a joint venture of the European aerospace company Airbus and the French group Safran, with its three core businesses: aerospace (orbital propulsion systems and equipment), defence and security with the objective of development and subsequent production of Ariane 6 .  The company was established by 1 January 2015, its headquarters is in Issy-les-Moulineaux near Paris. Singapore Technologies Aerospace (ST Aerospace) is a subsidiary of ST Engineering headquartered in Singapore, with international offices and facilities located in key aviation hubs in Asia Pacific, Europe and the US.  ST Aerospace started as a maintenance depot to support the Republic of Singapore Air Force in 1975.  Over the years, it has diversified into various MRO capabilities for commercial and military aircraft through strategic partnerships, acquisitions and investments.  The firm employs in excess of 8,000 certified engineers and administrative specialists around the world and has a global customer base that includes military forces, major airlines and freight carriers.  "Aviation Week" ranked the aerospace company as the world's largest, independent, third party airframe MRO provider with an annual capacity of more than 11.5 million commercial airframe man-hours in 2012. AD Aerospace plc is a British aerospace company based in Preston Brook, Cheshire.  It specialises in video security systems, safety systems and fire detection systems for airliners. Qinetiq ( as in "kinetic"; styled as QinetiQ) is a British multinational defence technology company headquartered in Farnborough, Hampshire.  It is the world's 52nd-largest defence contractor measured by 2011 defence revenues, and the sixth-largest based in the UK. The British Aerospace 146 (also BAe 146) is a short-haul airliner and a regional airliner that was manufactured in the United Kingdom by British Aerospace, later part of BAE Systems.  Production ran from 1983 until 2002.  Manufacture of an improved version known as the Avro RJ began in 1992.  A further-improved version with new engines, the Avro RJX, was announced in 1997, but only two prototypes and one production aircraft were built before production ceased in 2001.  With 387 aircraft produced, the Avro RJ/BAe 146 is the most successful British civil jet airliner programme. CAP Scientific Ltd was a British defence software company, and was part of CAP (Computer Analysts and Programmers)] Group plc.  In 1988, CAP Group merged with the French firm Sema-Metra SA in 1988 as Sema Group plc.  In 1991 Sema Group put most of its defence operations (CAP Scientific Ltd and YARD Ltd) into joint venture with British Aerospace called BAeSEMA, which British Aerospace bought out in 1998.  Parts of the former CAP Scientific are now BAE Systems Insyte). The aerospace industry of the United Kingdom is the fourth-largest national aerospace industry in the world and the third largest in Europe, with a global market share of 6.4% in 2016.  In 2013, the industry employed 84,000 people.  Domestic companies with a large presence in the British aerospace industry include BAE Systems (the world's third-largest defence contractor), Britten-Norman, Cobham, GKN, Hybrid Air Vehicles, Meggitt, QinetiQ, Rolls Royce (the world's second-largest maker of defence aero engines) and Ultra Electronics.  Foreign companies with a major presence include Boeing, Bombardier, Airbus (including its Astrium, Cassidian and Surrey Satellite Technology subsidiaries), Leonardo (including its AgustaWestland and Selex ES subsidiaries), General Electric (including its GE Aviation Systems subsidiary), Lockheed Martin, MBDA (37.5% owned by BAE Systems), Safran (including its Messier-Dowty and Turbomeca subsidiaries) and Thales Group (including its UK-based Thales Air Defence, Thales Avionics and Thales Optronics subsidiaries).  Current manned aircraft in which the British aerospace industry has a major role include the AgustaWestland AW101, AgustaWestland AW159, Airbus A320 family, Airbus A330, Airbus A340, Airbus A380, Airbus A400M, BAE Hawk, Boeing 767, Boeing 777, Boeing 787, Bombardier CRJ700, Bombardier CSeries, Bombardier Learjet 85, Britten-Norman Defender, Britten-Norman Islander, Eurofighter Typhoon, Hawker 800, Lockheed Martin C-130J Super Hercules and Lockheed Martin F-35 Lightning II.  Current unmanned aerial vehicles in which the British aerospace industry has a major role include BAE Taranis, HAV 304 Airlander 10, QinetiQ Zephyr and Watchkeeper WK450. Ruth Waller (born March 6, 1984 in Manchester, England) is an English elite middle distance runner who specializes in the 800 and 1500 metres.  She ran for McNeese State for three and a half years, with junior year spent mostly as a red shirt due to University related issues.  Her McNeese highlights were Southland Conference Champion in the 800m indoor and outdoor and the mile indoor.  With her one and a half years left of eligibility after graduating from Mcneese State, she ran for Baylor University and achieved All American in the Distance Medley Relay in 2007.  In Great Britain she is ranked 3rd All-time in the under 20 yrs of age 2000m and 3000m Steeplechase in 2003, and ranked 3rd All-time in the indoor mile in 2007.
Answer: London