Little Willie proves the concept before the Army takes over

Beginning in February 1915, the committee tested both wheeled and tracked vehicles. By July it had Little Willie working with a rear steering carriage, a practical result that brought the effort to the War Office's attention. Big Willie marked the move toward the rhomboid form associated with the Mark I, although only a grainy image was available to show it. Once the project looked likely to succeed, the Army pressed to take it over. In roughly five months the team had moved from no practical machine to prototypes substantial enough to trigger a struggle over institutional ownership.