Starting in 1844, the hill surrounding the tunnel was subject to extensive quarrying to extract Bath stone for buildings.

In the run-up towards the Second World War, the need to provide secure storage for munitions at distributed locations across the UK was recognised.
During the 1930s, a proposal to create three Central Ammunition Depots (CADs) was submitted: one in the north (Longtown, Cumbria); one in the Midlands (Nesscliffe, Shropshire); and one in the South of England at Tunnel quarry, Monkton Farleigh and Eastlays Ridge.

During the 1930s, Tunnel Quarry was renovated by the Royal Engineers as one of the three major stockpiles.
During November 1937, the GWR was contracted to build a 1,000-foot (300 m) long raised twin-loading platform at Shockerwick for Monkton Farleigh and two sidings branching from the Bristol–London mainline just outside the tunnel's eastern entrance at 51°24′19.31″N 2°17′22.94″W. Thirty feet (9.1 m) below and at right angles to this point, the War Office had built a narrow-gauge wagon-sorting yard which accessed  a 1.25-mile (2.0 km) tunnel, built by the Cementation Company, descending at a rate of 1 in 8.5 to the Central Ammunition Depot in the former quarry workings.
The logistics operation was designed to cope with a maximum of 1,000 tons of ammunition per day.

A Royal Air Force station, RAF Box, was established and used an area of the tunnels.
In response to the Bristol Blitz, during 1940, Alfred McAlpine developed a fallback aircraft engine factory for use by the Bristol Aeroplane Company (BAC), although it never went into production.
BAC used the facility to accommodate the company's experimental department, which was developing an engine to power bombers and the Bristol Beaufighter.

The CAD was closed at the end of the war but was maintained in operational condition until the 1950s.
The sidings were cleared, and saw no further use until the mid-1980s when a museum was opened on the site for a short period.
During the post-war years, portions of the ammunition depot were redeveloped for other facilities, including the Central Government War Headquarters, RAF No.1 Signal Unit, Controller Defence Communication Network and the Corsham Computer Centre.
As of the present day, the only element of the complex that remains is the former computer centre and the visible north end of the tunnel has been sealed by concrete and rubble.
The former CAD has been reused as a secure commercial document storage facility.
Starting in 1844, the hill surrounding the tunnel was subject to extensive quarrying to extract Bath stone for buildings.
In the run-up towards the Second World War, the need to provide secure storage for munitions at distributed locations across the UK was recognised. During the 1930s, a proposal to create three Central Ammunition Depots (CADs) was submitted: one in the north (Longtown, Cumbria); one in the Midlands (Nesscliffe, Shropshire); and one in the South of England at Tunnel quarry, Monkton Farleigh and Eastlays Ridge.
During the 1930s, Tunnel Quarry was renovated by the Royal Engineers as one of the three major stockpiles. During November 1937, the GWR was contracted to build a 1,000-foot (300 m) long raised twin-loading platform at Shockerwick for Monkton Farleigh and two sidings branching from the Bristol–London mainline just outside the tunnel's eastern entrance at 51°24′19.31″N 2°17′22.94″W. Thirty feet (9.1 m) below and at right angles to this point, the War Office had built a narrow-gauge wagon-sorting yard which accessed  a 1.25-mile (2.0 km) tunnel, built by the Cementation Company, descending at a rate of 1 in 8.5 to the Central Ammunition Depot in the former quarry workings. The logistics operation was designed to cope with a maximum of 1,000 tons of ammunition per day.
A Royal Air Force station, RAF Box, was established and used an area of the tunnels. In response to the Bristol Blitz, during 1940, Alfred McAlpine developed a fallback aircraft engine factory for use by the Bristol Aeroplane Company (BAC), although it never went into production. BAC used the facility to accommodate the company's experimental department, which was developing an engine to power bombers and the Bristol Beaufighter.
The CAD was closed at the end of the war but was maintained in operational condition until the 1950s. The sidings were cleared, and saw no further use until the mid-1980s when a museum was opened on the site for a short period. During the post-war years, portions of the ammunition depot were redeveloped for other facilities, including the Central Government War Headquarters, RAF No.1 Signal Unit, Controller Defence Communication Network and the Corsham Computer Centre. As of the present day, the only element of the complex that remains is the former computer centre and the visible north end of the tunnel has been sealed by concrete and rubble. The former CAD has been reused as a secure commercial document storage facility.
Box Tunnel