'Erecting Sheds', where aircraft were prepared for flight testing. They were for the most part referred to by personnel as the 'Flight Sheds'. CBAF's chief test pilot was Alex Henshaw MBE who managed a team of pilots who had the job of flight-testing the aircraft. The Air Transport Auxiliary were responsible for dispersing tested machines to the Maintenance Units around the country for the fitting of radio-telephones and other equipment. As any build-up of machines on the airfield would be vulnerable to aerial attack, testing was carried out during daylight in almost any weather. CBAF produced all versions of the Spitfire from the Mk II onwards. This aircraft had the more powerful Rolls-Royce Merlin XII engine, providing , an increase of over the Mk I, and could be used with either the de Havilland or Rotol propellers. The first Mk II flew on 24 September 1939. However, even as the first Spitfires were being built in June 1940, the factory was still incomplete and there were numerous problems with the factory management which ignored tooling and drawings provided by Supermarine in favour of tools and drawings of its own designs. Meanwhile, the workforce, while not completely stopping production, continually threatened strikes or "slow downs" until their demands for higher than average pay rates were met. By May 1940, Castle Bromwich had not yet built its first Spitfire in spite of promises that the factory would be producing 60 per week starting in April. It is worth noting, however, that key players, such as Alex Henshaw, viewed the problems as primarily those of poor management during the initial phase. Workers worked twelve-hour on and twelve-hours off until bombings forced a switch to a three-shift, eight-hour system. Henshaw attended the diamond jubilee in 1996 of the founding of the CBAF, hosted by Jaguar Cars Limited in the old factory and remained fulsome in his praise for the workforce until his death. Vickers-Armstrong: 1940–1945 After the fall of the government of Neville Chamberlain, new Prime Minister Winston Churchill appointed press tycoon Lord Beaverbrook as the Minister of Aircraft Production. On 17 May, Beaverbrook telephoned Nuffield and manoeuvered him into handing over control of the Castle Bromwich plant to Beaverbook's Ministry. Nuffield was furious and reported the incident to Churchill, but Beaverbrook countered by sending in aircraft expert Sir Richard Fairey who wrote a secret report which detailed how expensive machinery had been unused,