In 1936, the British government had formalised a plan under the Air Ministry called the Shadow factory plan, to increase capacity within Britain's aircraft industry. Headed up by Herbert Austin, the plan was to create nine new factories, and add additional capacity and facilities to Britain's existing car manufacturing plants to enable them to quickly turn to aircraft production, should the political situation in Europe change towards war.
In 1936 the Air Ministry purchased a parcel of land opposite Castle Bromwich Aerodrome, which encompassed an old sewage works. Developed and managed by the Nuffield Organisation, owners of Morris Motors LImited, they were briefed to manufacture Supermarine Spitfire fighters, and later Avro Lancaster bombers. The theory was that the local Birmingham skills-base and production techniques used in the manufacture of motor vehicles could be transferred to aircraft production.
CBAF ordered the most modern machine tools then available, which were being installed two months after work started on the site.
Although Morris Motors under Lord Nuffield (an expert in mass motor-vehicle construction) managed and equipped the factory, it was funded by government money. When the project was first mooted it was estimated that the factory would be built for £2,000,000, however, by the beginning of 1939 this cost had doubled to over £4,000,000. The Spitfire's stressed-skin construction required precision engineering skills and techniques outside the experience of the local labour force, which took some time to train. Aircraft and sub-assemblies were taken across the Chester Road to Castle Bromwich Aerodrome, though early plans included an aerial bridge from E block to the airfield.
Very large hangar-like buildings were erected on the east side of the airfield which were originally referred to as '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.
P8088, Spitfire Mk IIA, was built at Castle Bromwich
CBAF produced all versions of the Spitfire from the Mk II onwards. This aircraft had the more powerful Rolls-Royce Merlin XII engine, providing 1,150 horsepower (860 kW), an increase of 120 horsepower (89 kW) 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.