[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.

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

[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.

[9] In July 1915, 171st Tunnelling Company moved to Ploegsteert and commenced mining operations near St Yves at the southern end of the Messines ridge.

Difficult geology lead to two mines being abandoned before completion, and after a charge of 23,000 kilograms (50,000 lb) of ammonal had been put in place beneath the farm, the gallery was discovered by a German counter-mining operation on 24 August 1916.

[13] Three days later the German miners blew a heavy charge, which shattered about 120 metres (400 ft) of the main gallery and killed four men engaged in repairs.

Another shaft (Trench 122 Right) was started part way along the original tunnel and after another 200 metres (660 ft), a charge of 40,000 lbs of ammonal was placed by the Royal Engineers beneath the ruins of Factory Farm which sat on the German front line.

On 3 March the Germans blew the main tunnel with a heavy charge laid from their Ewald shaft, leaving it beyond repair and resulting in it being cut off for three months.

The Spanbroekmolen mine exploded 15 seconds late, killing a number of British soldiers from the 36th (Ulster) Division, some of whom are buried at Lone Tree Cemetery nearby.

Despite meeting clay and being inundated with water underground which necessitated the digging of a sump, they managed to complete a gallery stretching almost half a mile from the shaft in just two months, and a further charge of 14,000 kilograms (30,000 lb) of ammonal was placed.

In February 1917, German countermeasures necessitated some repair to one of the chambers and the opportunity was taken to place a further charge of 8,800 kilograms (19,500 lb) marking a total of four mines, all of which were ready by 9 May 1917.

[17] When it was detonated on 7 June 1915, the mine did not produce a crater but left a shallow indentation in the soft clay; the shock wave did great damage to the German position.

Needing shelter for their troops, the Allied High Command in January 1918 moved 25,000 specialist tunnellers and 50,000 attached infantry who had been preparing and taking part in the Battle of Messines north in the Ypres Salient.

There they dug almost 200 independent and connected structures at depths of 30 metres (98 ft) into the blue clay, which could accommodate from 50 men, to the largest at Wieltje and Hill 63 which could house 2,000.

[23] The level of the activity can be gauged by the fact that by March 1918, more people lived underground in the Ypres area than reside above ground in the town today.

[24] Created 14 metres (46 ft) below Flanders by the 171st Tunnelling Company,[25] and dug over a period of four months, the engineers used I beams and reclaimed railway line in a D-type sett structure.

[26] The Vampire dugout became operational from early April 1918, first housing the 100th Brigade of the British 33rd Division, then the 16th King's Royal Rifle Corps and then the 9th Battalion Highland Light Infantry Regiment.

In March 1918, the 171st Tunnelling Company constructed a deep dugout in the centre of Zonnebeke, located directly beneath the ruins of the parish church.

[28] Shortly after the completion of the Vampire dugout, 171st and several other tunnelling companies (173rd, 183rd, 184th, 255th, 258th and 3rd Australian) were forced to move from their camps at Boeschepe in April 1918, when the enemy broke through the Lys positions during the German spring offensive.