In 1910 Hornsby demonstrated its chain-track vehicle to the British Army, which subsequently bought four caterpillar tractors to tow artillery. At this demonstration, a British transport officer suggested putting armour plating and a gun on a Hornsby tractor, thus creating some sort of self-propelled gun. David Roberts, Managing Director of Hornsby, did not pursue the idea, but later expressed regret at not having done so. Four years later, Hornsby sold the patent for its caterpillar track to the Holt Manufacturing Company of California, USA, for $8,000, having itself sold only one caterpillar tractor commercially. The Holt system was superior to Hornsby's, but the Hornsby transmission was what Holt really wanted. Thanks, in part, to this acquisition, Holt eventually became the successful Caterpillar Inc. Tractor Company.