In the 1920s, British engineers explored the idea of an SPG on a tank chassis. Development of the vehicle started in 1923 at the Royal Arsenal, Woolwich. It was based on the Vickers Medium Mark II, the chassis of which could carry the required modules. A total of seven prototypes were manufactured from 1926 through 1927 and joined the Experimental Mechanised Force established on May 1, 1927. Later, the unit was disbanded, along with the SPG program. Time for the successive autoreloading of each shell into the magazine. Characteristics are specified for Siege mode. Characteristics are specified for Rapid mode. Reload time of the first and second guns on double-barreled vehicles. Characteristics are specified for vehicles with crews trained to 100%.