An elaborate trench network was dug around the St Eloi craters by the Germans, with a front line west of the craters and a reserve line to the east; the 46th Reserve Division held the new line until it was moved south to the Somme in August.
In March 1916, 172nd Tunnelling Company handed its work at St Eloi over to the 1st Canadian Tunnelling Company and mining operations at St Eloi continued.
The largest mine at St Eloi was begun by the Canadian tunnellers on 16 August 1915, with a deep shaft named Queen Victoria,  dug near Bus House Cemetery behind a farm-house called Bus House by the British troops (50°48′46.8″N 2°53′13.6″E).
From there, the gallery was extended to the area of the mine chamber and the chamber was set 42 m (138 ft) below ground, at the end of a gallery 408 m (1,339 ft) long and charged with 43,400 kg (95,600 lb) of ammonal by 11 June 1916.

For the Battle of Messines in 1917, the British began a mining offensive against the German lines along the ridge to the south of Ypres.
Twenty-six deep mines were dug by Tunnelling companies RE, most of which were detonated simultaneously on 7 June 1917, creating 19 large craters.
The joint explosion of the mines in the Battle of Messines was one of the largest ever non-nuclear explosions.
 When the large St Eloi deep mine was fired by the 1st Canadian Tunnelling Company on 7 June 1917, it destroyed craters D2 and D1 from 1916 but the double crater H4 and H1 can still be seen.
The detonation was followed up by the 41st Division, which captured the German lines at St Eloi.
An elaborate trench network was dug around the St Eloi craters by the Germans, with a front line west of the craters and a reserve line to the east; the 46th Reserve Division held the new line until it was moved south to the Somme in August. In March 1916, 172nd Tunnelling Company handed its work at St Eloi over to the 1st Canadian Tunnelling Company and mining operations at St Eloi continued. The largest mine at St Eloi was begun by the Canadian tunnellers on 16 August 1915, with a deep shaft named Queen Victoria,  dug near Bus House Cemetery behind a farm-house called Bus House by the British troops (50°48′46.8″N 2°53′13.6″E). From there, the gallery was extended to the area of the mine chamber and the chamber was set 42 m (138 ft) below ground, at the end of a gallery 408 m (1,339 ft) long and charged with 43,400 kg (95,600 lb) of ammonal by 11 June 1916.
For the Battle of Messines in 1917, the British began a mining offensive against the German lines along the ridge to the south of Ypres. Twenty-six deep mines were dug by Tunnelling companies RE, most of which were detonated simultaneously on 7 June 1917, creating 19 large craters. The joint explosion of the mines in the Battle of Messines was one of the largest ever non-nuclear explosions.  When the large St Eloi deep mine was fired by the 1st Canadian Tunnelling Company on 7 June 1917, it destroyed craters D2 and D1 from 1916 but the double crater H4 and H1 can still be seen. The detonation was followed up by the 41st Division, which captured the German lines at St Eloi.
Actions of St Eloi Craters