wing, needed due to the demands of the engine's cooling system. The wing lacked flaps, a requirement for the aircraft to land at safe speeds. Unofficially named the Spitfire, the Type 224 first flew on February 1934. The aircraft looked clumsy, and was inefficient, in part because the cooling system failed to prevent the engine from overheating. The RAF decided that the Type 224's performance was unsatisfactory, and selected the Gloster Gladiator in preference. Supermarine Spitfire Whilst the Type 224 was still being built in 1933, Mitchell was proceeding with the design of the Type 300. This was to become his masterpiece, the Supermarine Spitfire. He cleaned up the design of the Type 224, using the same engine but incorporating a shorter wing and a retractable undercarriage. The Air Ministry rejected Mitchell's design, but he modified it, for instance by making the wing thinner and shorter, by including the newly-designed Rolls-Royce Merlin engine, and by making use of an innovative new cooling system—the latter being an example of his willingness to accept ideas from other people. For a short period, design work continued using private funding, but in December 1934 the Air Ministry contracted Supermarine to construct a prototype that was based on Mitchell's design. Mitchell objected to the Air Ministry's insistence that the Spitfire be modified to have a tail wheel. At the time he was not told that, in preparation for a future war, the government had decided to build hard surface runways for the RAF, a decision that meant the modification to the Spitfire was necessary. The prototype, given the serial K5054, first flew on 6 March 1936, at Eastleigh, Hampshire. Mitchell witnessed the flight. Despite being ill, he travelled to Eastleigh during the flight tests for K5054. In June 1936, before the prototype had completed being trialled, the Air Ministry placed an order for 310 Spitfires. Many of the technical advances in the Spitfire were made by people other than Mitchell: the thin elliptical wings were designed by the Canadian aerodynamicist Beverley Shenstone, and the Spitfire shared similarities with the Heinkel He 70 Blitz. The under-wing radiators had been designed by the Royal Aircraft Establishment, and monocoque construction had been first developed in the United States. Mitchell's achievement lay in the merger of these different influences into a single design, originating from his "unparalleled expertise in high-speed flight... and a brilliant practical engineering ability, exemplified in