In 1946, Specialised Armour Development Establishment (SADE) engineers created a modification of the Cromwell V capable of carrying RP-3 air-launched rockets, designated Cromwell V (RP-3), also known as the Cromwell "Tulip". Four fixed rails were mounted on a welded frame along the sides of the turret. Standard RP-3 rockets, designed for destroying submarines and ships, but widely used in practice for assaulting ground targets, were mounted on these rails. After a cycle of tests, the Cromwell "Tulip" remained on the proving ground as a single prototype. A similar method was attempted to arm the Sherman Firefly.

Introduced in Update 1.59 "Flaming Arrows", the Cromwell V (RP-3) is very similar to the Cromwell V in terms of armour, mobility, and armament. The 75 mm gun can help do damage to tanks of the same class like the Panzer IV, using its speed to get to an angle to hit the weaker points of the enemy tanks. However, the Cromwell RP-3 is equipped with four rockets on the turret. Unlike contemporaries such as the T34 Calliope, which often have the rockets on racks above the turret, the rockets integrated alongside the turret allows for easier and more reliable aiming. For ranges of around 500 m, the rockets can be aimed by use of the gun's aiming sight. Though practice is needed to get the feel of the rocket's landing point, this is a lot better than simply lobbing rockets after rockets in hope that one will hit.