The A43 Black Prince was the name assigned to an experimental development of the Churchill tank with a larger, wider hull and a powerfull Ordnance QF 17-pounder gun. It was named after Edward, the Black Prince, a famous 14th century military leader. It is so heavily armored, it can bounce the 88mm projectiles from a Tiger it's front.
As a development from the Churchill, the Black Prince was a continuation of the line of Infantry tanks, that is slower, heavier tanks intended to operate in close support of infantry. The parallel development in British tank design were the Cruiser tanks, which were intended for more mobile operations. A43 was the General Staff Specification number issued in 1943, for an interim tank that would eventually be superseded by a "Universal tank" that would replace both Infantry and Cruiser tanks.
The cruiser line led to the Cromwell tank (and the 17 pounder armed Challenger variant) and then the Comet tank, (which had a variant of the 17 pounder gun) entering service during the war. While not as heavily protected as the Churchill, the Comet showed the way tank development was going. This led to the last of the cruiser line and the first of the Universal tanks, the very successful Centurion tank.
A larger gun than a conventional Churchill required a larger turret on a wider turret ring and consequently a widening of the tank hull to carry this. The Black Prince weighed around ten tons more than the Churchill so the suspension was modified and the tracks widened by 10 inches to carry the extra load. However, the Churchill's 350-horsepower (260 kW) engine was retained, leading to the tank being underpowered and slow, with maximum speeds of 10.5 mph (16.9 km/h) on roads and 7.5 mph (12.1 km/h) cross country. This was so slow that the tank's tactical usefulness would have been limited. Consideration was given to the use of the Rolls-Royce Meteor engine; this would have increased the available power to 600 hp (450 kW), but the idea never left the drawing–board. Likewise, plans to fit the Black Prince with the turret from the Centurion were never carried out.
By the time the Black Prince prototypes had appeared in May 1945, the Sherman Firefly had acquired a proven combat record, the Comet tank was in service and the introduction of Centurion was imminent. All these tanks carried the QF 17-pounder or a derivative; all had better mobility than the Black Prince and the Centurion had frontal armour of comparable effectiveness. The Black Prince had become redundant and the project was abandoned.
The Black Prince marked the end of the development of the Churchill tank, and the end of the Infantry tank concept in British tank design.