The Rolls-Royce Avon powered the English Electric Lightning fighter.
The Avon was an axial-flow turbojet developed by Rolls-Royce after the Second World War. The English Electric Lightning used two Avon engines mounted one above the other in its fuselage, an unusual arrangement that helped preserve the fighter's slim profile while providing the thrust needed for high-speed interception.
The Lightning became the first and only British fighter capable of sustained flight at twice the speed of sound in level flight. Its performance depended on the combination of aerodynamic design, afterburning engines and a carefully integrated intake and fuselage layout.
The Avon powered many other aircraft, including the de Havilland Comet and certain Canberra variants, so identifying it solely with the Lightning can be misleading. Conversely, the Lightning should not be confused with the Harrier, whose vertical-takeoff capability came from the Rolls-Royce Pegasus turbofan rather than the Avon turbojet.