Mitchell as was his wont commenced in July 1934 designing what he hoped would be a much improved fighter, which was given the designation Type 300. It was much better streamlined than the Type 224, with a shorter wing, retractable undercarriage and an enclosed cockpit. Mitchell continued to evolve the design, striving for the maximum performance he could get from the engine and airframe combination. In November 1934 the design was further revised to accommodate the promising new Rolls-Royce PV.XII (PV-12) engine, which was later named the Merlin. The estimated performance of the new design was such that McLean approved in November 1934 expenditure on detailed design of a prototype, as he was confident that funding of a prototype was extremely likely from what was a supportive Air Ministry. Within a month of receiving the initial data, the Air Ministry issued specification F.37/34 to cover the construction of a prototype Type 300. Given the name Spitfire by the Vickers board, the prototype Type 300 when it first flew on 5 March 1936 at nearby Eastleigh airport marked a revolutionary advance for the RAF. The Air Ministry was so impressed that on 3 June 1936 it ordered 310. The earlier Hawker Hurricane and the Spitfire were the mainstay of RAF Fighter Command fighter aircraft which fought off the Luftwaffe bombing raids with fighter escorts during the Battle of Britain in the summer of 1940. While the Hurricane was available in larger numbers and consequently played a larger role, the new Spitfire became adored by both the public and its pilots and became the aircraft associated with the battle. It went on to play a major part in the remainder of the war, in a number of variants and marks, and it was the only allied fighter aircraft to be in production through the entirety of the Second World War. It went out of service in 1954. Increasing production capacity At the time of receiving its first order for the Spitfire the company did not have the management skills, organisation tools and physical space as this one order was more than double the total number of aircraft they had built in the previous 20 years. As a result, much of the work had to be sub-contracted to other firms, which led to chaos with drawings and the delivery of parts. To compound the problem skilled sheet-metal workers were in short supply. Supermarine