The Siddeley S.R.1 was a British experimental aircraft developed in the 1950s. It was designed to explore the capabilities of vertical takeoff and landing (VTOL) technology, which allows an aircraft to take off and land vertically. The S.R.1 featured a unique design with rotating engines that enabled it to transition between vertical and horizontal flight. The aircraft was part of a broader effort during the Cold War to enhance military aviation capabilities. Although the Siddeley S.R.1 did not enter production, it contributed valuable data to the development of future VTOL aircraft, influencing designs like the Hawker Siddeley Harrier.