Even as the English Electric "Canberra" jet-powered light bombers were entering service in the 1951, it was already being suspected by British authorities that the system would have run its course as soon as the mid-1950s. The design was based in 1940s technology and thinking and Soviet advances in missiles and interceptors quickly led to the West rewriting their approach to various aspects of aerial warfare multiple time. Nevertheless, this steady bomber managed an extensive service career with the Royal Air Force (RAF) that spanned into 2006 (by which time they were being used in the reconnaissance role) and other examples went on to serve under the banners of global players that included Australia, India, and Peru.
Against this backdrop, a successor was being sought out during the middle and latter half of the 1950s that led to several of the prominent British aero-industry players lending their talents by submitting proposals of various types. Supermarine Aviation Works, which was already able to sell the Royal Navy on its "Scimitar" single-seat, twin-engine carrier-based fighter (introduced in 1957), looked to fulfill the new need by taking this same design through an extensive modification process to produce a viable, tactically-minded light-class bomber. The result was a proposal based around the "Type 565" to fulfill "Operational Requirement 339" ("OR.339").
Design work began in February of 1957 and involved a reworking of the existing Scimitar airframe. The nose was reformed in an effort to better house a new radar fit, in this case the unit was to be the ARI.5390 "Blue Parrott" based in the AI.23 "Airpass II" work (proposed for "OR F.155" interceptor requirement) and intended for low-altitude work. Because of the Scimitars single-seat design, the fuselage was widened to accommodate a second crewman in the new side-by-side cockpit arrangement - communication and shared workload between the two crew would be key. As the new aircraft was no longer required to operate from British carrier decks, the arrestor gear, wing-folding feature and other naval-centric qualities were removed in the redesign for simplicity. Additionally, the one-time fighter design lost its 4 x 30mm ADEN internal cannons to improve internal fuel loads (and therefore help to increase operational ranges).
Each wing mainplane was now redesigned to carry four underwing hardpoints instead of the original two and the members were each also given support for conformal fuel tanks to further address operational range. There was also an in-flight refueling probe added to the starboard side of the nose section.
Proposed armament was 6 x 1,000lb conventional drop bombs, all to be held externally, or, in their place, a single nuclear-tipped drop bomb under the port side wing offset by a 200 gallon fuel drop tank under the starboard side wing.
For power, engineers settled on 2 x Rolls-Royce RA.24 "Avon" axial-flow turbojet engines to supply the needed power. The units were to be aspirated through half-moon, side mounted intakes and exhausted through traditional rings found along each side of the tail unit. Rocket-Assisted Take-Off (RATO) was to have been optional by way of a de Havilland "Spectre" rocket booster providing an additional 8,000lb of thrust. Estimated top speed was near 715 miles-per-hour with a range out to 1,095 miles. Maximum Take-Off Weight (MTOW) was to reach just under 50,000lb with a full nuclear weapon load out and fuel load - making for one heavy combat aircraft.
Beyond this, the aircraft was to have a running length of 37.1 feet and a wingspan measuring 61.5 feet. The fuselage was streamlined rather well from nose-to-tail and sweepback was apparent along all wing leading and trailing surfaces (including the tail). The tail unit retained the Scimitar's single-finned configuration with downward-canted horizontal planes. Its retractable tricycle undercarriage was also to be reused.
In any event, the design was not selected and furthered, remaining a "paper airplane" for its time in British aviation history. It fell under review, along with several other submissions, in May of 1957, but was not seen as the proper solution mainly due to promised performance, weapons capability, and perceived development / procurement costs when weight against other entries. To add to this, the Defence White Paper review of 1957 also went on to doom many manned aircraft projects - not helping matters in the slightest.