The RAF issued requirement F1/55 in 1955 to initiate the development of the next generation air intercept plane to replace the English Electric Lightning. The performance required by the aircraft was extremely demanding, and to satisfy the requirement, the British aerospace industry submitted a selection of weird and wonderful designs. The requirement was won by a design from the second tier firm, Fairey. Despite building some important planes over the preceding decades, Fairey were not backed by a large industrial conglomorate, so were seen as a second tier firm. With their Delta I and Delta II planes they had achieved a stride on competitors with practical knowledge of supersonic delta aircraft.