Powered by an Armstrong Siddeley Screamer rocket for take-off, and the same company’s Viper turbojet for its return to base, the Avro 720 was designed to fulfil OR.301 of 1952 for a mixed-powerplant interceptor. One airframe, given the serial XD696, was nearing completion when the 720 programme was cancelled during 1955-56.

The mid-fifties saw the Saunders-Roe SR.53, which mated a Viper turbojet and a Spectre rocket, and the Avro 720, with a similar turbojet and a Screamer rocket (on photo), proposed as a means of countering the advances that were being made by Soviet manufacturers in the development of high subsonic and transonic bombers.