After the SP70 project to develop a European self-propelled gun failed in the 1980s, Vickers Shipbuilding and Engineering Limited (VSEL) started developing its own artillery system. The company aimed to meet demand in both the UK and overseas. The designers' concept was similar to that of the Marksman anti-aircraft system — to create a universal turret that could be mounted on any tank chassis. This would enable obsolete tanks to be modernised at a lower cost than purchasing fully-fledged self-propelled guns. The designers selected the FH-70 gun as the primary weapon. The resulting turret, the GBT 155, could be mounted on the Vickers Mk.3, Chieftain, Centurion and Challenger chassis. However, it failed to attract buyers. Development of the turret continued, and a modernised version was used for the AS90 and the Polish AHS Krab.

The GBT 155 was introduced in Update 2.55 "Ninth Wave". It is a fairly fast self-propelled gun with a powerful cannon and a good reload rate. However, it has a large silhouette and the turret only provides reliable protection against rifle-calibre machine guns. Additionally, the turret is full of ammunition which often detonates on penetration.