In 1881 the hills on the North Western side of Monkton Farleigh village were quarried for Bath Stone. By the time the quarries closed in 1930 the whole of the hill was riddled with roughly 300 acres of tunnels.

During the build up to WW2 the War Department decided that there was a need for a large underground ammunitions store. It was decided that the required space could be obtained by converting four quarries, these four formed what was collectively known as the Central Ammunitions Depot Corsham. Monkton Farleigh mine was acquired and became the biggest of the four sub components, a total of two and a half million square foot was converted.

The three other sub-depots were Tunnel Quarry at Corsham, Eastlays Quarry at Gastard and nearby Ridge Quarry.

Extensive conversion work was carried out at Monkton Farleigh, existing slope shafts were adapted and four new slope shafts were sunk. Above each of these slope shafts and loading shed building was built. Two service hatches and many air shafts were driven down in to the workings.

The site was served by an aerial rope way which transported the ammo cases from the main GWR line at Ashley. The rope ways needed to be replaced due to it’s vulnerability to attacks from air. A straight tunnel was bored stretching over a mile underground between Monkton and Farleigh Down Sidings.

The depot was gradually completed and filled with ammunition district by district until it’s completion in 1941, it was able to hold up to 120,000 tons of ammunition.

Huge amounts of funds were pumped in to the site after the war to maintain it’s condition until 1960 when it was decided to be surplus. The site was run down over the next few years while the last of the ammunition was depleted.