de Havilland Gyron
The Gyron was designed in 1951 by de Havilland as a private venture supersonic turbojet. The Gyron was first run in a test bed on 5th January 1953. Flight tests began in 1955 in a Short Sperrin under a Ministry of Supply contract. The engine was never put into production, losing out to the Bristol Siddeley/Rolls-Royce Olympus.