design was the Merlin aero engine, which was first flown in prototype form in 1935, although he had died in 1933. This was developed from the R engine, which had powered a record-breaking Supermarine S.6B seaplane to almost in the 1931 Schneider Trophy. The Merlin was a powerful supercharged V12 engine and was fitted into many World War II aircraft: the British Hawker Hurricane, Supermarine Spitfire, de Havilland Mosquito (twin-engine), Avro Lancaster (four-engine) (a development of the Avro Manchester with its unreliable Rolls-Royce Vulture engines), Vickers Wellington (twin-engine); it also transformed the American North American P-51 Mustang into a competitor for the best fighter of its time, its engine a Merlin engine built by Packard under licence. Over 160,000 Merlin engines were produced, including over 30,000 by the Ford Motor Company at Trafford Park, Manchester. During the war most Rolls-Royce flight testing of engines was carried out from Hucknall Aerodrome. The Merlin crossed over into military land-vehicle use as the Meteor powering the Centurion tank among others. Many Meteor engines used engine blocks and parts that failed requirements for high performance engines, but were suitable for use in the derated Meteor. In December 1942, over a "five-shilling meal" at the Swan and Royal in Clitheroe, Stanley Hooker and Ernest Hives of Rolls-Royce agreed with Spencer Wilks of the Rover Car Company that Rolls-Royce would take over top secret work on the development of the jet engine. An exchange of assets followed with Rover and in the post-World War II period Rolls-Royce made significant advances in gas turbine engine design and manufacture. The Dart and Tyne turboprop engines were particularly important, enabling airlines to cut times for shorter journeys whilst jet airliners were introduced on longer services. The Dart engine was used in Armstrong Whitworth AW.660 Argosy, Avro 748, Fokker F27 Friendship, Handley Page Herald and Vickers Viscount aircraft, whilst the more powerful Tyne powered the Breguet Atlantique, Transall C-160, Short Belfast, and Vickers Vanguard, and the SR.N4 hovercraft. Many of these turboprops are still in service. Amongst the jet engines of this period was the RB163 Spey, which powers the Hawker Siddeley Trident, BAC One-Eleven, Grumman Gulfstream II and Fokker F28 Fellowship. During the late 1950s and 1960s there was a significant rationalisation of all aspects of British aerospace and this included aero-engine manufacturers. In 1966 Rolls-Royce acquired Bristol Siddeley (which had resulted from the merger of Armstrong Siddeley and