Few families of research aircraft tell the story of post-war British aviation ambition quite as vividly as the Avro 707 series — a collection of five diminutive jets that helped lay the foundations for one of the most iconic bombers ever to take to the skies. The origins of the Avro 707 are intertwined with those of the Avro Vulcan: in the late 1940s, the high-speed characteristics of delta-shaped wings were relatively well understood theoretically, but little was known about their behaviour at low speeds, where various aerodynamic factors made analysis very difficult. Aerodynamically a one-third scale version of the Vulcan, the prototypes were ordered by the Ministry of Supply to Specification E.15/48, with production accelerated by using components from other aircraft — the canopy of the first prototype taken from a Gloster Meteor. 

On 4 September 1949, the first Avro 707, VX784, performed its maiden flight from RAF Boscombe Down with Squadron Leader Samuel Eric Esler at the controls. Tragedy followed almost immediately: on 30 September 1949, just weeks after its debut, the aircraft crashed near Blackbushe, killing Esler — the subsequent investigation concluding that a suspected control circuit failure had caused the air brakes to lock open, provoking a stall. Work continued regardless. The second prototype, VX790, was rebuilt as the 707B, featuring a longer nose, an alternative cockpit canopy, a modified wing with 51° sweep, and an elongated nose wheel leg for a greater angle of incidence during landing and take-off; it first flew on 6 September 1950 and quickly proved to be relatively docile in flight. Flight testing from Dunsfold soon justified Avro's faith in the delta wing and its relatively docile handling characteristics, restoring the confidence that the crash of VX784 had shaken.

The third aircraft, the 707A, took the programme to the next level. Built for higher-speed testing, the 707A moved the engine intakes from the dorsal spine to the wing roots — experience with the earlier aircraft having shown that as speed increased, cockpit-induced turbulence interrupted the intake airflow. When the Vulcan appeared, it looked very much like an enlarged 707A, and later the 707A was used to test the compound leading edge sweep subsequently used on all Vulcans. Two 707As were eventually built, resplendent in bright orange and silver natural metal finishes respectively. The final variant, the two-seat 707C, was originally conceived to perform delta wing orientation training for the Royal Air Force; the sole prototype, WZ744, made its maiden flight on 1 July 1953 and was ultimately employed in research that did not involve Vulcan development at all. Its most substantial research contribution was to the development of fly-by-wire control systems — one of the first aircraft of its kind to be so fitted — and it was also equipped with a side stick controller.

All five Avro 707 aircraft provided valuable insights into delta wing flight characteristics, most of the information coming from the second and third prototypes which flew before the Vulcan itself. Even after the Vulcan development phase was concluded, the four surviving 707 variants — resplendent in individual bright blue, red, orange and silver colour schemes — continued to play significant roles as research aircraft, spending time at the Royal Aircraft Establishment carrying out handling trials, particularly in the field of powered controls. The Avro 707 family gave British aircraft designers early confidence in the general handling characteristics of the delta wing, which led to its adoption on other aircraft types, and some of the systems tested found direct application on other military aircraft programmes. Three of the five survive in museums today — quiet monuments to the courage of the test pilots who flew them, and to the engineers whose work in these small, colourful jets helped give Britain the Vulcan.