Following the failure of the F7/30 Type 224 fighter, Vickers-Supermarine Chief Designer R.J. Mitchell determined to design what he believed would be the answer to the need of a short-range high speed intercepter. When the design was submitted to the Air Ministry in July 1934, it was rejected for being too radical.

          Mitchell then revised the design and in November 1934 convinced the Board of Directors of Vickers to fund construction of the project as a private venture. Freed of the obtuseness of official specifications, he had created the most modern fighter design then in existence, to be powered by the new Rolls-Royce PV-XII V-12 engine, later named the "Merlin".  The design was designated the Type 300.  Many of us believe it to be aesthetically the most beautiful airplane ever made. 

           Once it was known that Vickers would support construction of the prototype with their own money, the Air Ministry finally took notice of what was happening and  the Air Ministry issued contract AM 361140/34, which provided £10,000 for the construction of what was called the "improved F7/30 design."

           Construction of the Type 300 began in December 1934.  On January 3, 1935, the Air Ministry issued a new specification, F10/35, which was written around the aircraft, and a serial number was issued, K5054. In April 1935, the armament was changed from two .303 Vickers machine guns in each wing to four .303 Brownings, following a recommendation by Squadron Leader Ralph Sorley of the Operational Requirements section at the Air Ministry.  The prototype was completed at the end of February 1936, and the first flight came on March 5, 1936, at Eastleigh Aerodrome, with Vickers Chief Test Pilot Joseph "Mutt" Summers at the controls, who is quoted as saying "Don't touch anything" on landing. The eight-minute flight occurred four months after the maiden flight of the contemporary Hurricane, which had also begun life as a private venture as the "Fury monoplane."

           Minor modifications and refinements were made to the Type 300 as the result of flight trials over the following months. Fitted with a new propeller, Summers again flew K5054 on March 10, 1936, retracting the undercarriage for the first time.  A new PV-12 was fitted after the fourth flight, and further test-flying became the responsibility Summers' assistants, Jeffrey Quill and George Pickering., who soon discovered the Type 300 was very good, but not perfect. The rudder was over-sensitive and the top speed was just 330 mph, only a little faster than the Hurricane. The rudder was redesigned and a new and better-shaped wooden propeller resulted in an increase in top speed to 348 mph.  In  mid-May, K5054 to the RAF  Aeroplane & Armament Experimental Establishment (A&AEE)at Martlesham Heath, where Flight Lieutenant Humphrey Edwardes-Jones took over testing for the RAF.  His only request was that the airplane be equipped with an undercarriage position indicator.  On June 3, 1936, the Air Ministry placed an order for 310 Spitfires.

           On March 22, 1937, during performance trials at Martlesham Heath, K5054 suffered an oil pressure failure and was damaged during a belly landing. On September 4, 1939, the day after Britain declared was on German, K5054 nosed over on landing at the Royal Aircraft Establishment at Farnborough.  The  fuselage was intact, but the cockpit was crushed and pilot F/Lt White died of injuries caused when the mast, mounted on the fuselage behind the pilot, was pushed down through the fuselage and pulled the Sutton seat harness back with such force that he bent the back of the seat on impact with it.  The Type 300 was written off as a total loss.

          The director of Vickers-Armstrongs, Sir Robert MacLean, had guaranteed production of five aircraft a week, beginning 15 months after an order was placed, when the prototype contract was finalized in February 1935. On June 3, 1936, the Air Ministry placed an order for 310 aircraft, for a cost of £1,395,000.  While full-scale production began at Supermarine's factory in Southampton, it quickly became clear the order could not be completed in the 15 months promised, since Supermarine was a small company, busy building Walrus and Stranraer flying boats, and Vickers was busy building the Wellington.  As a result of the delays in production, the Air Ministry suggested that production of the Spitfire be stopped after completion of the initial order for 310, after which Supermarine would build Bristol Beaufighters.  The compnay convinced the Air Ministry the problems could be overcome.  On March 24, 1938, a second contract for 200 Spitfires was signed, the two orders covering the K, L and N prefix serial numbers. The first production Spitfire rolled off the assembly line in May 1938, and was flown by Jeffrey Quill on May 15, 1938, almost 24 months after the initial order. The final cost of the first 310 aircraft, after delays and increased costs, came to £1,870,242 or £1,533 per aircraft more than originally estimated.  A production Spitfire I cost £9,500; the most expensive components were the hand-fabricated and finished fuselage at £2,500, the Rolls-Royce Merlin engine at £2,000, the wings at £1,800 a pair, guns and undercarriage at £800 each, and the propeller at £350.