Despite defense spending getting heavily cut after WWI, work to perfect existing vehicle didn't stop. One of the directions which British engineers developed was mechanization of artillery. The war showed that the army needs tracked tractors capable of quickly transporting artillery on the march and on the battlefield. Wheeled tractors were unsuitable for the harsh terrain of a WWI battlefield. Tracked tractors like the Holt 75 were also suboptimal due to their low speeds.
Two relatively new players faced off on this arena. Vickers began work on the 18-pdr Transporter, and Sir W.G. Armstrong Whitworth & Co. Ltd. designed a vehicle called Dragon (from "drag gun"). The concept of the vehicles was similar. The gun rolled into the transporter during the march, and the crew sat inside, facing each other. Both vehicles were ready in 1922. Further work on the 18-pdr Transporter led to the creation of the Light Tank Mk.I, which later evolved into the Medium Tank Mk.I.