Comparing: FV201 (A45) vs. O-Ni

Developed starting in 1944 by English Electric as a possible replacement for the A43 Black Prince. Some components were unified with the A41 Centurion. In 1948 trials of a prototype were started. The prototype mounted a Centurion Mk. II turret and a 17-pounder gun. Due to changes in Armored Forces policy and doctrine, development proceeded no further. However, the design later served as a basis for several post-war heavy tanks.

A further development of the O-I with improved anti-tank guns. The military command's plan was to improve the earlier models and achieve a higher level of armor protection on the vehicle. Existed only in blueprints. No finished prototypes were built and the vehicle never saw action.