Development of the Centurion Action X began in the early 1950s. The aim of the project was to improve the Centurion’s ballistic protection by fitting the vehicle with the recently developed ‘mantletless’ turret design. The turret was fitted on a Centurion Mk.7 hull and featured thick, heavily sloped surfaces which further increased its effectiveness.

Furthermore, the vehicle was tested with both the QF 20-pdr as well as the 105mm L7 cannon. In the end however, only a couple prototypes were built and tested in addition to a few turrets being used separately for ballistic trials. The Centurion Action X never passed the testing stage and was thus also not ordered into production. However, the experience gained during its development, specifically regarding the use of the mantletless turret, was later incorporated into subsequent tank designs such as the FV4202 and the well-known Chieftain main battle tank.