Monkton Farleigh Quarry

Overview

Bath stone workings begun in 1881 that left some three hundred acres of tunnel under the hill behind Brown's Folly by the time quarrying stopped in 1930. Converted into a sub-depot of Central Ammunition Depot Corsham and served by a mile-and-a-quarter tunnel and conveyor from the railway below, it became one of the biggest underground ammunition stores of its kind; it now holds documents.

History

The hills on the north-western side of Monkton Farleigh village were quarried for Bath stone from 1881, and by the time the quarries closed in 1930 the whole of the hill was riddled with roughly three hundred acres of tunnels. That void was the asset the War Office wanted. In the rearmament of the later 1930s the quarry was converted into a sub-depot of Central Ammunition Depot Corsham, and when it was built it was one of the biggest of its kind anywhere. The difficulty was getting to it: the mine lies on the top of a hill just behind Brown's Folly, with poor road access. At first it was served by an aerial ropeway running some two miles down the hill to sidings at Farleigh Down. That was replaced by one of the more remarkable pieces of engineering in the English stone country - a tunnel of a mile and a quarter driven by the Cementation Company from the sidings up to the depot, descending at one in eight and a half. Ammunition was loaded from train to conveyor at the bottom; narrow-gauge trucks ran down from the platform into the tunnel, where a heavy-duty conveyor belt carried the load directly to the storage gallery it was meant for. The depot outlived its purpose and found another. The site is now used for secure document storage, several of its districts leased by a security company, which has kept them from further decay.

Geology

Worked the Bath stone freestone of the hill north-west of Monkton Farleigh, the same Jurassic oolitic limestone mined across the Corsham plateau, whose wide unsupported roof span leaves large galleries behind the working.

Workings

Underground stone workings covering roughly three hundred acres of tunnel under the hill. After conversion the depot was reached by an aerial ropeway of about two miles down to Farleigh Down sidings, replaced by a tunnel a mile and a quarter long descending at one in eight and a half, worked by narrow-gauge trucks feeding a heavy-duty conveyor belt that ran ammunition to the storage galleries. Ventilation was by large vertical intake and exhaust shafts.

Closure

Stone working ended in 1930, after which the workings were taken for military storage as a sub-depot of Central Ammunition Depot Corsham.

What remains

In commercial use as secure document storage. Most of the original surface features remain, though some buildings have been demolished and the survivors are in poor condition, with a large section of roof lost in recent years. The present owners have repurposed some of the exit shafts as intake and exhaust for a new ventilation system, while most of the original airways are disused with the remains of their fans still in place. Districts 19 and 20 remain derelict.

Most of the depot's original surface buildings, in poor condition, together with the vertical ventilation shafts of the wartime system and the inclined entranceways now used as air intakes.

Related mines

• Tunnel Quarry, Corsham — Both were Bath stone workings taken for Central Ammunition Depot Corsham in the rearmament of the 1930s; Tunnel Quarry was the principal depot and Monkton Farleigh a sub-depot.

Nearby mines

• Box Quarry — 3.2 km N
• Combe Down Stone Mines — 6.2 km SW, Somerset
• Tunnel Quarry, Corsham — 6.2 km NE
• Monks Park Mine — 7.6 km E
• Dunkerton Colliery — 10.8 km SW, Somerset

Straight-line distance, within 15 km. Show on the map.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• The hills on the north-western side of Monkton Farleigh village were quarried for Bath stone from 1881, and by the time the quarries closed in 1930 the whole of the hill was riddled with roughly three hundred acres of tunnels. ¹
• The mine stands on the top of a hill behind Brown's Folly with poor road access, and was served at first by an aerial ropeway running some two miles down to Farleigh Down sidings. ²
• The ropeway was replaced by a tunnel a mile and a quarter long, built by the Cementation Company and descending at one in eight and a half from the depot to the sidings. Narrow-gauge trucks ran down from the platform into the tunnel, where a heavy-duty conveyor belt carried the ammunition to the appropriate storage gallery. ²
• Monkton Farleigh was once one of the biggest ammunition depots of its kind. The site is now used for secure document storage, most of the original surface features remaining though the buildings are in poor condition; some exit shafts have been repurposed as intake and exhaust for a new ventilation system, and districts 19 and 20 remain derelict. ¹

Photographs & further reading

Sources

1. (secondary) Monkton Farleigh Ammunition Depot — Subterranea Britannica
2. (secondary) Farleigh Down Tunnel — Subterranea Britannica

Record created: 23 September 2026 · Last researched: 23 September 2026