In spring of 1917, 173rd Tunnelling Company added a deep dugout to the existing trench.

The completed Yorkshire Trench dugout then served as headquarters for the 13th and 16th Battalions of the Royal Welch Fusiliers at the start of the Battle of Passchendaele later that year.

[4] The BEF had decided to carry out all operations in the offensive of summer 1917 from deep dugouts.

[5] The condition of the ground made digging the deep dugouts extremely difficult and dangerous.

Work had to be carried out silently and secretly, facing an observant enemy who was only a few hundred metres away.