P.1 by English Electric. On 29 March 1949 MoS granted approval for English Electric to start the detailed design, develop wind tunnel models and build a full-size mockup. The design that had developed during 1948 evolved further during 1949. To achieve Mach 2 the wing sweep was increased to 60° with the ailerons moved to the wingtips. In late 1949 low-speed wind tunnel tests showed that a vortex was generated by the wing which caused a large downwash on the tailplane; this issue was solved by lowering its height below the wing. Hence, by late 1949 the basic configuration of the P.1A Lightning was fixed. By late 1949 the relationship between Sheffield's Preston Strand Road engineering works and Petter's design team at Warton had deteriorated. Modifications to the Canberra to incorporate a bomb aimer, camera bays and dual seat for the navigation trainer required a redesign of the front fuselage, which caused disruption in the design office and the workshops. In addition, with the P.1A Lightning design programme ramping up, Petter demanded a separate administration for Warton and an experimental workshop under his control as a condition of his continued service with English Electric. Sir George Nelson was unable to reach a compromise acceptable to both Petter and Sheffield. Page tried to persuade Petter to stay by promising to help in dealing with Sheffield. From December 1949 Petter ceased to take an active part in running Warton, he visited Warton once again to speak to a few people and clear his office. Page took over the day-to-day management until in February 1950, Petter resigned and Page was formally appointed his successor. The Lightning remains the only all-British Mach 2 aircraft. Folland Aircraft In the late 1940s Folland Aircraft Limited in Hamble, Hampshire was manufacturing sub-assemblies for other aircraft manufacturers. Henry Folland planned to retire and recruited Petter as chief engineer and deputy managing director. Petter joined Folland in September 1950, succeeding Henry Folland as managing director in July 1951. Although Petter had entered into an anti-poaching agreement with English Electric, a number of his ex-colleagues joined Folland when positions were openly advertised. With a strong team, led by a designer of Petter's pedigree, Folland was now able to win MoS design contracts, such as that for the development of the Red Dean air-to-air missile in mid-1951. On 11 July 1951 a delegation from the RAF visited Petter to discuss the