[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.

1st Australian Tunnelling Company took over in November 1916 and maintained the completed mines beneath Hill 60 and The Caterpillar over the winter and months of underground fighting until June 1917, when they were fired at the beginning of the Battle of Messines.

[citation needed] After the German spring offensive in April 1918, when the enemy broke through the Lys positions, the 3rd Canadian Tunnelling Company were put on duties that included digging and wiring trenches over a long distance from Reningelst to near Saint-Omer.

[1] The operation to construct these fortifications between Reningelst and Saint-Omer was carried out jointly by the British 171st, 173rd, 183rd, 184th, 255th, 258th, 3rd Canadian and 3rd Australian Tunnelling Companies.