Armstrong Siddeley Sapphire  Wright J65
Armstong Siddeley Viper Bristol Siddeley Viper Rolls Royce Viper

Armstrong Siddeley got its start in aircraft engines when the Siddeley-Deasley Motor Car Company was given the task of producing the BHP and RAF.8 engines in 1917. After redesign, these became the Siddeley Puma and Jaguar engines.
In 1919, Armstrong Whitworth purchased the company to form Armstrong Siddeley Motors (ASM). ASM produced excellent smaller engines during the 20s and 30s; however, their big engines lacked power and reliability. In 1935, ASM became part of the Hawker Siddeley Group.

After World War II, the company focused on turboprop engines. The most important post-war ASM engine was the Sapphire turbojet.

In 1958, the Ministry of Supply used the TSR.2 contract to enforce mergers. In order to bid on the contract, Armstrong Siddeley Motors merged with Bristol Aero-Engines in 1959 to form Bristol Siddeley Engines Ltd.