(8) The wheels of the cruiser should be on either the “Pedrail” system or the “Caterpillar” system; whichever is the most suitable for crossing marshy and slippery ground.
Most of these requirements had already been embodied in the wooden model of Big Willie, which, when completed, was inspected at Wembley on September 28. This model was accepted as a basis on which construction was to proceed, it was in fact the first “mock up” of the eventual Mark I machine.
Big Willie was about 8 ft. high, 26 ft. long, and 11 ft. wide without sponsons, and 3 ft. wider when these were added. His armament consisted in two 6-pounder guns and two machine-guns, and the crew suggested was 1 officer and 9 other ranks.
On the following day the “Joint Committee” assembled at the Admiralty and decided that the following specifications should be worked to: weight 22 tons, speed 3½ miles per hour, spanning power 8 ft., and climbing power 4½ ft.
On December 3, Mr. Churchill addressed a paper to G.H.Q., entitled “Variants of the Offensive,” in which he accentuated the necessity of concentrating more than we had done on “the attack by armour,” the chief purpose of armour being to preserve mobility. He suggested the combined use of the caterpillar tractor and the shield. The caterpillars were to breach the enemy’s line and then turn right and left, the infantry following under cover of bullet-proof shields. It was further suggested that the attack might be carried out at night under the guidance of searchlights. The rest of this paper dealt with “Attack by Trench Mortars, Attack by the Spade, and The Attack on the First Line.”
On Christmas Day 1915, Sir Douglas Haig, who had recently taken over command of the Expeditionary Force in France, read this paper, and wishing to know more about the caterpillars mentioned, Lieutenant-Colonel H. J. Elles (later on G.O.C. Tank Corps) was sent to England to ascertain the exact position. On January 8 this officer reported in writing to G.H.Q., as follows:
“There are two producers of landships:
“(a) Trench Warfare working alone.[14]
“(b) The Admiralty Landship Committee working with the War Office.
“The first have not yet made a machine, but its proposed size is 10 ft. high, 14 ft. 6 in. wide, and 36 ft. long; the second was in process of being made” (i.e. Big Willie).