The BAC 221 is one of the most fascinating transformations in British aviation history — a world air speed record holder reborn in the service of the most ambitious civil aviation project Britain ever undertook. The BAC 221 was a development of the Fairey Delta 2 supersonic research aircraft; the Filton division of the British Aircraft Corporation carried out an extensive modification programme on the former world speed record holder, fitting new ogival delta wings similar in shape to those designed for Concorde, along with revised control surfaces, new air intakes, a variable droop nose, and new undercarriage. On 1 May 1964, the modified aircraft performed its first flight. As a result of the flight testing conducted by the BAC 221, the ogee delta wing was subsequently adopted for the Concorde supersonic transport airliner. The majority of the BAC 221 flight test activity was carried out at the Royal Aircraft Establishment at Bedford, where it completed a total of 273 flights. The sole BAC 221 is now displayed alongside the first British-built Concorde and the Handley Page HP.115 at the Fleet Air Arm Museum at Yeovilton — a fitting tribute to the aircraft whose curved wing shaped the most iconic airliner ever built.