[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.

The number of units available to the BEF was also restricted by the need to provide effective counter-measures to the German mining activities.

[4] 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.

[5] 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 New Zealand Tunnelling Company arrived at Plymouth on 3 February 1916 and was deployed to the Western Front in northern France.

[6] A Canadian unit was formed from men on the battlefield, plus two other companies trained in Canada and then shipped to France.

[7] Immediately after its formation, 170th Tunnelling Company was rushed to Givenchy for operations to counter enemy mining activity in that sector.

In the opening of the Battle of Loos (25 September – 14 October 1915), the unit blew two mines at the Hohenzollern Redoubt.

[1] The Hohenzollern Redoubt near Loos-en-Gohelle in the Nord-Pas-de-Calais region of France was the site of intense and sustained fighting between German and Allied forces.

After an earlier British attack in October 1915, extensive tunnelling had been conducted by the Germans during the winter of 1915–1916; due to the nature of the clay covering and chalk below ground, mine explosions threw up high lips around mine craters, which became good observation points.