The galleries were first constructed 5 feet high by 3 feet wide, as anything smaller would not allow a man to swing a pick properly. It was found, however, that the clay was so hard and tough that a pick could not be driven into it more than a couple of inches, and this would only dislodge a small piece on the end of the pick. Progress was painfully slow, until the sewer men came to the rescue and taught us clay kicking. In this, an instrument shaped like a small spade – very strong, with a razor edge and heavy shoulders – known as a push pick was used. In operation, the miner sat on the floor with a pile of sand bags behind him to give him purchase. By putting both feet on to the shoulders, he would work the blade into the face and then, by pushing the handle upwards, bring out the clay in chunks. The bottom cut was awkward, but after that the rest of the face was brought out with ease and rapidity. This method, besides being quicker, was much more silent and allowed us to reduce the size of the gallery to 3ft 10ins x 2ft 4 ins. When our men became expert in this method an average day’s drive was 25 to 30ft. It was in this respect we were far ahead of the enemy. His galleries were far cleaner and better timbered than ours, but his best speed was 6 feet per day. (Anon. Officer, 250 Tunnelling Company)⁵

The British regarded the German and French close-timbering of galleries as excessive, and accused the Germans of working by the book and lining all their galleries with timber regardless of whether the ground required it. Timbering had the advantage of lessening the damage caused by camouflets, but slowed progress and required a lot of wood. The German officer quoted above stated that, for the system opposite Givenchy-lès-la Bassée, where they were indeed necessary, 12,000 to 15,000 mining frames were used for close-timbering (as well as 500,000 sandbags for removing the spoil).⁶ Again the New Zealanders claimed superiority in their lack of timbering, but this was nothing special when set alongside the British, Australian and Canadian tunnellers, who all knew what the ground required for particular conditions. In the most extreme conditions of the deep Messines mines, where the galleries had to support perhaps 100ft of wet sand, and the clay expanded on exposure to moisture, 250 Company found that the standard 9in by 3in timbers shattered, and they replaced them with 6in to 8in pit props with 6in by 4in timbers, and eventually spaces were left between the mining sets to allow for the expansion. At this depth 5in by 3in steel girders were also used to support the galleries.⁷

The British and Commonwealth units regarded their speed as superior to the French and Germans, and there is no doubt that speed was one means by which they were able to obtain an advantage over the Germans. There was also a strong rivalry for footage between Tunnelling Companies, with frequent claims of record speeds through clay or chalk. The fact that the expertise resided in the companies rather than the command in respect of tunnelling practice was acknowledged by the leeway that the British gave units. Information was distributed in ‘Mining Notes’, which described practice as carried out by companies so that experience might be shared. Any pre-war information about military mining was quickly discarded by the British, even to the extent that the trade of ‘miner’ was replaced by that of ‘tunneller’ and the units were known as Tunnelling Companies. In the French and German armies, the pre-war instructions were still used as the basis for underground warfare. The extracts from the old mining regulations, which the Germans reissued in 1915, having excluded them from those issued in 1911 and 1913, contained some practices which were still relevant, but caused the Germans to be hidebound. Likewise, in 1915 the French thought too much in terms of traditional siege warfare methods of classical sapping and shallow mining attacks as a response to trench warfare. The British were willing to allocate very large numbers of men to mining and a tunnelling company might exceed 900 men, including the attached infantry for carrying spoil. By the middle of 1916 the British had 25,000 men employed on underground work.⁸ Yet the workings in the most active area in 1916, on the 1st Army front around Loos, were never used in a major offensive and resulted in underground stalemate.