[2] Following consultations between the Engineer-in-Chief of the BEF, Brigadier George Fowke, and the mining specialist John Norton-Griffiths, the War Office formally approved the tunnelling company scheme on 19 February 1915.

[3] To make the tunnels safer and quicker to deploy, the British Army enlisted experienced coal miners, many outside their nominal recruitment policy.

These companies each comprised 5 officers and 269 sappers; they were aided by additional infantrymen who were temporarily attached to the tunnellers as required, which almost doubled their numbers.

[2] The success of the first tunnelling companies formed under Norton-Griffiths' command led to mining being made a separate branch of the Engineer-in-Chief's office under Major-General S.R.

[4] The formation of twelve new tunnelling companies, between July and October 1915, helped to bring more men into action in other parts of the Western Front.

The intention was to employ this unit, which was at that time about 1,000 strong, with the ANZAC at Gallipoli, but instead it was moved to France in May 1916, where it also appeared as the "Australian Mining Battalion".

The mines placed under the German lines by the 3rd Canadian Tunnelling Company had already been charged with explosives by the time the Australians arrived in the area.

[1][6][7] Drainage and ventilation shafts had to be dug in the unfamiliar blue clay, and there was a constant danger of collapse, particularly in the part of the gallery leading to The Caterpillar, which passed under the railway line.

The Official Australian History states that at Hill 60, "underground warfare reached a tension which was not surpassed anywhere else on the British front".