In the quest to supply the British Royal Air Force (RAF) with a new, Mach 2-capable all-weather, high-altitude interceptor/fighter, many industry players attempted to satisfy the service's requirement known as "Operational Requirement F.115T" (or OR F.115T). F115T was formed from discussions had by authorities during the mid-1950s and was formally drawn up on January 15th, 1955 - the goal to counter the threat being posed by Soviet supersonic high-altitude, nuclear-capable bombers with a design replacing the in-service Gloster Meteor and Javelin jet fighters. The result was a bevy of designs put forth during the period that would emerge from the usual defense industry players like Armstrong Whitworth (AW), de Havilland (DH), English Electric (EE), Hawker, and Fairey.
The requirement was centered on a powerful performer able to meet any inbound aerial threat head-on. This meant multiple jet engines (and even rocket propulsion) figured into the mix to provide the needed Rate-of-Climb (RoC) as well as dashing speed while specific attention needed to be paid to overall aerodynamic design intended to reach the Mach 2 flight envelope. This advanced aircraft would also have to support "Airborne Interception" (A.I.) radar in its nose and most likely a crew of two to spread out the workload. The radar would be mated to a complete weapons system that had yet to be developed and perfected, a system centered on the delivery of capable Air-to-Air Missiles (AAMs).
All this would have to be made operational by a 1962 deadline.
For Fairey engineers, one submission intended to fulfill the role was based in the existing single-seat, single-engine "Delta 2" experimental research aircraft of 1954 - this single-engine product was completed and flown through two examples and collected important data on supersonic flight. It was decided to rework this design, retaining its relatively compact footprint and as many existing components as possible, to expedite delivery of the new RAF Mach 2 interceptor-fighter. For Fairey, the new design was known as "E.R.103".
Traits to be carried over in E.R.103 were the single-seat cockpit, single-engine installation, and the unique ability for the nose section to "tilt down" (aka "droop-nose") along a hinge when the aircraft was running along the ground, taking-off, or coming in for a landing to help increase pilot vision.
The engine would be buried in the aft-section of the fuselage, aspirated by rectangular intakes located along the sides of the fuselage and exhausting through a singular circular port under the tail. The nose section would house the radar fit (this to become a Ferranti A.I.23 series unit) with the cockpit positioned just aft. Views were to be obscured some by the framing of the canopy as well as the elevated fuselage spine aft of the position. The wing mainplanes would become large-area surfaces of delta form which negated use of horizontal tailplanes and provide wingtip hardpoints for the carrying of one AAM per wing member. A single vertical fin would be set over the tail section. Ground-running was to be accomplished via a retractable tricycle arrangement with a lengthened nose leg giving the aircraft a pronounced "nose-up" attitude when on the ground.
At this point it was seen that the missile-of-choice would become the "Blue Jay" Mk.4 series AAM.
Power stemmed from a single de Havilland "Gyron" afterburning turbojet engine of unknown thrust output and this would be paired with 2 x de Havilland "Spectre" rocket boosters for short bursts of performance power. Engineers estimated a maximum speed around Mach 2.5 at operational altitudes reaching between 60,000 and 90,000 feet with all systems engaged. As such, cockpit pressurization and an ejection seat was a must as well as titanium construction for the temperatures produced at such high-speeds/high-altitudes.
This early F.155 project entry was ultimately passed on by British authorities leading Fairey to draw up plans for a much larger interceptor-fighter along the same lines (again to expedite final delivery). This form incorporated a twin, side-by-side engine arrangement again augmented by rocket-boosting performance - a combination of 2 x Rolls-Royce RB.122 (enlarged versions of the earlier RB.106 series units) or DH Gyron afterburning turbojets with 2 x Spectre rockets. Like the earlier E.R.103, and the Delta 2 research plane before it, this enlarged F.155T proposal would have used the droop-nose function for close-to-ground actions. Missile-carrying was now moved to underwing hardpoints from the wingtips as this offered better, stronger support for heavier missiles.
Like the E.R.103, the newer F.155T offering was also rejected by authorities before the end and all work on manned fighters was halted after the 1957 defense review (the "Defence White Paper" of April 1957) due to the perceived onset of the "Missile Age". The review irreparably damaged British aero-industry with many major brand names more or less forced to merge capabilities.