Much like its contemporary, the US M103, the Conqueror was designed as a heavy tank capable of matching the Soviet IS-3 and T-10 during the immediate post-war years. As such, it was fitted with the same 120-mm gun of the M103, as well as heavy armor protection although this in turn raised the weight of the vehicle significantly, compromising mobility. Additionally it was seen as mechanically unreliable despite relatively good cross-country performance, even when compared with the lighter Centurion. Among its innovations was a rotating commander's cupola, which allowed for target alignment independently of the turret (through a coincidence rangefinder). Conquerors served only with the British Army and were deployed in Germany, providing long-range fire support to Centurions. Eventually, the fitting of the 105-mm L7 gun on the Centurion rendered the Conqueror obsolete and these were eventually phased out in 1966.

The Conqueror was derived from the A45 infantry support tank developed in 1944. The design was eventually used for the FV 200 series of Universal Tanks, with a common hull for various different vehicles including self-propelled artillery and APC. Fitting of a Centurion Mk. 2 turret (with a 17-pounder gun) resulted in the FV 221 Caernarvon Mk. 1, and this was later upgraded to a 20-pounder in the Mk. 2. These only served for trials before being fitted with a 120-mm gun and redesignated FV 214 Conqueror Mk. 1 and Mk. 2, the latter with improved armor plate joints. A small number of FV 222 Conqueror ARV (Armoured Recovery Vehicle) were also produced.