Swinton recounts in his book "Eyewitness" how he first got the sudden idea to build a tank on 19 October 1914, while driving a car in France. It is known that in July 1914 he received a letter from a friend, a mining engineer named Hugh F. Marriott whom he had met while in South Africa. Marriott occasionally sent Swinton news of technical developments that might have a military application, and his letter described a machine he had seen in Antwerp, an American-made Holt Caterpillar Tractor. He suggested that the machine might be useful for transport, and Swinton passed the information on to several military and political figures who he thought might be interested. At the time, with no apparent prospect of war, the idea seemed to be a matter only of transport efficiency, and Swinton forgot about the matter. The idea of a caterpillar track as the basis for a fighting vehicle occurred to him only as he drove from St. Omer to Calais on the morning of 19 October.