The Theseus was the Bristol Aeroplane Company's first attempt at a gas-turbine engine design. A turboprop delivering just over 2,000 hp (1,500 kW) was chosen rather than compete with companies that were already developing turbojets. A heat exchanger to transfer waste heat from the exhaust to the compressor exit was necessary to meet a requirement for a fuel consumption comparable to a piston engine. However, the heat exchanger was abandoned after tests showed that it had a high pressure loss and only produced a fuel saving of 8%. Furthermore overall performance was reduced

The Avro Type 694 Lincoln is a British four-engined heavy bomber, which first flew on 9 June 1944. Developed from the Avro Lancaster, the first Lincoln variants were initially known as the Lancaster IV and V; these were renamed Lincoln I and II. It was the 2nd last piston-engined bomber operated by the Royal Air Force (RAF).