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
Siddeley Engines Ltd.