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Royal Navy Propellant Factory, Caerwent

The Royal Navy Propellant Factory, Caerwent, Monmouthshire, UK, (later RAF Caerwent) was dedicated to the manufacture of explosives or the storage of ammunition from 1939 to 1993.

It is a large military site and is situated north of the A48 road four miles west of Chepstow and 12 miles (19 km) east of Newport. Since 1993 it has been used for a variety of military and civil purposes, including field exercises, car rallying, storage and breakdown of railway vehicles, and nature preservation. The site has its own standard gauge railway system (linked to the national network), many private roads and a wide range of buildings, from small earth-banked stores to large four storey lightly-built brick buildings. It is about two miles (3 km) east-west, and 1.5 miles (2 km) north-south. The perimeter road inside the security fence is, on its own, over seven miles long.


RN propellants factory 1939 to 1965

The site was created as a Royal Navy propellants factory in 1939.

Note: The Royal Navy Propellant Factory, Caerwent, like the Royal Navy Cordite Factory, Holton Heath, were never part of the Ministry of Supply/Royal Ordnance Factory management chain; they were controlled by the Admiralty. However, they were functionally very similar to Explosive ROFs.

In the summer of 1936 the site requirements for a new factory were drawn up. The main priorities were:

  • the establishment should not be vulnerable to air attack;
  • should not be located in an industrial area, but sufficiently close to a populated area to provide an adequate workforce;
  • should be close to a railway and to main roads;
  • should be located on rough grassland with a gravel on sand subsoil with good natural drainage and a slope of about 1 in 30 to provide maximum safety in the highly dangerous nitroglycerine manufacturing and handling areas;
  • the higher part should not have an elevation of not less than 100 ft. (30 metre) above the lowest part to limit the internal gradients.

Like all explosive factories of this type, a capacious supply of water was required for use in the manufacturing processes. To manufacture 150 tons of cordite per week the factory would need 3 million imperial gallons (14,000 m³) of drinking quality water per day.

In the final quarter of 19th century, the Great Western Railway (GWR) had undertaken the engineering feat of constructing the Severn Tunnel. One of the major difficulties encountered underground was the 'Great Spring', which necessitated the pumping of over 9 million gallons (41,000 m³) of water per day at Sudbrook from the western end of the tunnel, conveniently located only three miles (5 km) away from the proposed site at Caerwent. Even during the great drought of 1934 the lowest daily return was 9.1 million imperial gallons (41,000 m³). The GWR used about 1.5 million imperial gallons (6,800 m³) per day themselves, so there was always a guaranteed daily surplus of 7.5 million imperial gallons (34,000 m³).

The total area acquired was 1,580 acres (6.39 km²) of land, a total of 1,163 acres (4.7 km²) were enclosed within the factory fence. It was connected to the Great Western railway near Sudbrook by way of a private branch line, sometimes known as the MoD Caerwent sidings; and a number of transfer sidings were laid out inside the factory fence.

The site consumed the village of Dinham which was located at the northern edge of the RNPF Caerwent.

By the end of 1940 the Main Office block was complete, and in December of that year the Unit 1 Sulphuric Acid Factory went into production with acid mixing for the Nitrocellulose and Nitroglycerine manufacturing. Five months later, the Pressure Oxidation Plant for the manufacture of Nitric acid came on stream. In August 1941 the Nitrocellulose and Nitroglycerine plants were operational and were soon working 24 hours a day on a three-shift pattern. At the same time, Unit 2 of the factory was almost completed, so RNPF Caerwent was now virtually operational.

A total of £4.7 million was spent on buildings and roads, and £2.5 million on plant and equipment.

Early in the 1960s a Parliamentary working party recommended that propellants for the three branches of the armed services should be concentrated at the Royal Ordnance Factory at Bishopton. The decision to close RNPF Caerwent was announced on the 25 March 1965. Production continued during the following two year rundown phase.

Weapons storage 1967-1993

RAF Caerwent was transferred to US administration after De Gaulle expelled the US military from France in 1967. Caerwent thus became part of the US Army European 'theatre reserve stocks' under the command of the United States Army's "47th Area Support Group Reserve Storage Activity", with an Royal Air Force Liaison Party also present.

The US Army spent over £4 million constructing 300 magazines and converting some of the former RNPF structures to conform to the required specification. The material stored included small arms ammunition, artillery shells (up to 8"), anti-tank mines, grenades, flares and the multiple launch rocket system. The first shipments of shells, rockets, mines, flares and small arms ammo arrived early in 1968. Maintenance facilities were added in 1971.

In the early 1970s the site's capacity was expanded substantially, which allowed the closure of three other munitions bases in the West Midlands (Bramshall, Ditton Priors and RAF Fauld) in 1973. One of the reasons Caerwent was retained was its proximity to Barry Docks where many of the armaments entered the United Kingdom.

At its height Caerwent was the largest ammunition supply depot in Western Europe, storing over 80,000 tonnes of conventional munitions. In 1990 Caerwent shipped 12,000 tons of ammunition to the Middle East and played a critical part in Operation Desert Shield and Desert Storm.

Following the change in the political climate in Europe and subsequent scaling down of operations, the US Army announced it was to close down their storage operations at the establishment in June 1992. Over 60,000 tonnes of munitions were moved out over a period of less than ten months. The last batch was removed by train on the 19 July 1993. The formal closure ceremony took place on the 20 August 1993.

Present day

The base is now maintained by a small army staff as a 'Training Area' for troops from Beachley barracks and further afield. A 'representative sample' of the bomb storage and processing structures of this vast site can now be seen on the latest Ordnance Survey map showing roughly 200 structures. Previous editions showed the site as completely blank, but serviced by a railway line.

Caerwent is now a major training area covering over 1,500 acres (6 km²), capable of sustaining up to 1,000 troops. There are not only over 400 buildings and bunkers on the site, but also an operating railway and a comprehensive road system, for logistics exercises and driver training.

The site has been used for military training and public order training by various police forces. Local farmers are allowed to graze their livestock on the convenient areas of pasture that separate the former factory buildings.

Parts of the site have also been let for civilian usage, including driver training and car rallying run by Forresters Car Club and South Wales Automobile Club.

Since the privatisation of British Rail, RNPF Caerwent like a number of other MOD sites with internal railway sidings, has been used as a secure storage area for holding surplus locomotives and rolling stock that might be returned to use. A small number of electric locomotives, particularly in the British Rail Class 86 and British Rail Class 87, have been scrapped at RNPF Caerwent; also, British Rail Mark 2 carriages.

See also

  • 'The Factory' A history of the Royal Navy Propellant Factory, Caerwent by Medwyn Parry
  • Subterranea site visit with photographs
  • Multimap map and aerial imagery
  • Aerial photograph 1999


  • Bowditch, M.R. and Hayward, L., (1996). A pictorial record of the Royal Naval Cordite Factory, Holton Heath. Wareham: Finial Publishing. ISBN 1-900467-01-1.
  • Cocroft, Wayne D., (2000). Dangerous Energy: The archaeology of gunpowder and military explosives manufacture. Swindon: English Heritage. ISBN 1-85074-718-0.
  • Walker, Thomas A., (1888). The Severn Tunnel: Its Construction & Difficulties: 1872 - 1887. Republished 2004. Stroud: Nonsuch Publishing. ISBN 1-84588-000-5.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Royal_Navy_Propellant_Factory,_Caerwent". A list of authors is available in Wikipedia.
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