This mine was started by 250 Tunnelling Company in December 1915. The TC was commanded by Captain Cecil Cropper a metal mining engineer from Northumberland. His HQ lay within the Canadian Corps at La Clytte, and he had been ordered by Brigadier-General Charles Armstrong, Canadian Chief Engineer, to come up with an aggressive plan to counter the German mining on his front. Cropper had concluded that it was no use trying to sink shafts in the front or support trenches. He went further back to where the blue clay formation was at a depth that they could reach. He concealed the shaft in a wood in order to hide the works from the Germans and was successful in sinking the shaft down to the blue clay. The Germans at this point were holding a defensive position on the high ground at Spanbroekmolen. He concluded that it would take a gallery of some 250 to 300 yards to get below the objective and a very large explosion in a deep charge.
They succeeded in getting the shaft down 60 feet and had driven the gallery 90 feet by the end of January 1916 when they handed the mine over to the 3rd Canadian Tunnelling Company. By April the gallery had been driven forward 790 feet when he Canadians handed over to 175 Tunnelling Company. They stayed less than three weeks before handing over to 171 TC. Despite the constant changing of units the gallery had advanced to 1,717 feet reaching its objective on 28 June 1916 and was charged and wired ready for detonation.
Disaster strikes
With the delay in the Second Army attack that was to take place in 1916, a second shaft was started with the ambition to drive 1,200 feet and target the German strong point at Rag Point. At 665 feet the tunnellers from 171 TC went down to 120 feet below the surface and by mid-February 1917, the gallery had been driven 1,140. It was at this moment that the Germans blew a camouflet, although this did very little damage other than to dent the confidence of the tunnellers. It also told the British that the Germans had deep mined shafts in this area. The drive went on and had reached the trench known as Narrow Trench when the Germans blew another camouflet this time damaging some 500 feet of the incline and some of the main gallery. With the loss of the mine at La Petit Douve fresh in the mind of Major Henry Hudspeth, commanding 171 TC, it was 171 TC that the Germans had disturbed at that location, he decided not to retaliate with a counter-mine of his own as this would have given away his position. He decided to abandon this second drive.
The Germans were not done. On 3 March they blew a further camouflet and this damaged 400 feet of the gallery and cut the main wiring leads. Hudspeth put on his anti-gas Proto set and with another officer, a trained Proto set expert, went forward to inspect the damage. As they were observing the damage the other officer collapsed and died from the effects of the gas explosion, there was a leak in his equipment. Having completed his inspection Hudspeth concluded that the 40 ton mine had been lost. He ordered a new gallery to be started to run alongside the damaged old one knowing that the Germans could blow another camouflet that would crush, gas or bury the men alive working at the face.
By the end of April 1917, the gallery had been driven 1,429 feet and was close to the point where the Germans had blown their camouflet when gas was encountered and this got worse as they drove on with three men being overcome by the gas. The British installed a gas tight stopping and diverted the gallery to the right to go round the gas obstacle. They eventually reached the old chamber and rather than try to repair the leads they placed 1,000lb of dynamite against the main charge of 91,000 lbs of ammonal along with a new set of leads and completed 400 feet of tamping. This new mine was ready just hours before zero on 7 June 1917. The mine was fired by Hudspeth and Captain Francis Thornton.
The mine was blown 15 seconds late on 7 June and this resulted in the attacking infantry from the 36th (Ulster) Division, who had already left their trench to begin their advance, being thrown off their feet with a number being killed by the falling debris from the explosion. They are buried in the nearby Lone Tree Cemetery.
The bunker on the outer edge of the crater rim is where four dead German officers were found with no apparent marks or wounds. They had been killed by the concussion of the mine explosion.
