Site Records


Site Name: Lords Bridge (FFD4) Forward Filling Depot

Cambridge Road
Nr. Barton, Cambridgeshire
OS Grid Ref: TL391536

Sub Brit site visit 16th December 2003

[Source: Nick Catford]

Lords Bridge Forward Filling Depot is located in the south east corner of what was the Lords Bridge Air Ammunition Park, a forward ammunition depot for the RAF which opened on the 16th November 1939. The ammunition park comprised of a series of revetted magazines for the storage of high explosive and incendiary bombs. The forward filling depot, which opened in 1944, was a bulk storage and charging facility for filling 65lb light case bombs with mustard gas. After closure in 1957 the ammunition park was sold to Cambridge University where the Cavendish Laboratory established the Mullard Radio Astronomy Observatory (MRAO). This was sponsored by Mullard Ltd. and supported by the Particle Physics & Astronomy Research Council. The work of the MRAO was recognised by the award of the 1974 Nobel Prize for physics to Professor Ryle and Professor Hewish.

Plan of the Lords Bridge Air Ammunition Park showing the Forward Filling Depot in the south east corner.

Initially the University didn't use the forward filling depot which, in 1993, was being used as a proving ground for fireworks. The RAF had retained the area around the bulk storage tanks. This was finally handed over to the Defence Land Agents in July 1997 once the storage tanks and been excavated and infilled and the site had been thoroughly decontaminated and the land was gifted to the University. The whole site, including Lords Bridge Station and a section of the Bedford - Cambridge railway line (closed on 1st January 1968) on the northern perimeter has now been incorporated into the observatory.

The chemical name for mustard gas is dichlorodiethyl sulphide. At normal temperature it is a liquid, rather like diesel oil in appearance with a smell similar to garlic. It was used as a war gas because it is a 'vesicant' which means that contact with the liquid or vapor will cause blisters on the skin similar to third degree burns and if inhaled will cause serious damage to the lungs which will almost inevitable cause death. Its value in conflict was due to the fact that it does not decompose and will remain active in the ground or on materials it has contaminated for many days, in fact months or even years. This makes it completely different from the effects of chlorine or phosgene which, as gasses, are readily dissipated in the atmosphere.

Photo:The charging building with a covered way linking to the bonding building (out of picture) left and the empty storage building to the right. The structure in the foreground is the top of the emergency water supply tank.
Photo by Nick Catford

It is comparatively easy to manufacture given a supply of raw materials which are mostly readily available chemicals and there are really only two effective ways of decontaminating material or ground; one is by the application of bleaching powder and the other by burning.

There are two types of mustard gas, Runcol (HT) which is produced by the method used by the Germans in WW1 by reacting thiodiglycol (known as 'Syrup' during the war) with hydrochloric acid and Pyro (HS) which is produced by combining ethylene with sulphur dichloride. Runcol was more expensive to manufacture and was not suitable for tropical storage.

Chemical warfare was developed in Germany in 1915 but the allies were quick to respond with their own production and in the later years of WW1 mustard was used by both sides. Although chemical weapons were banned by the Geneva Protocols of the 1920's this did not stop their use by the Japanese in 1931 and the Italians in 1935 and even Churchill supported their deployment during WW2. With the coming of the war it was decided that the manufacture of chemical weapons should once again be undertaken to act as a deterrent as Germany would almost certainly be producing them.

Aerial photograph of Lords Bridge FFD
The position of the pots is clearly visible

Mustard gas was produced by ICI from 1938 at their Randle plant on Wigg Island near Runcorn in Cheshire and initially weapons were filled or 'charged' at Randle. It soon became clear that a safe storage facility was required for these weapons and in 1939 work started building the Valley Works at Rhydymwyn in North Wales.

In 1941 it was proposed that five forward filling depots (FFD) should be constructed and they were ready for use by 1944, the layout of these five depots is very similar. The five depots were:

FFD 1 Little Heath Suffolk Under the control of 94 Maintenance Unit
FFD 2 Melchbourne/Riseley Bedfordshire American FFD - Station 572
FFD 3 Norton Disney Lincolnshire Under the control of 93 Maintenance Unit
FFD 4 Lords Bridge Cambridgeshire Under the control of 95 Maintenance Unit
FFD 5 West Cottingwith/Escrick Yorkshire Under the control of 80 Sub Maintenance Unit

Construction of Forward Filling Depot 4 (Lords Bridge) began in March 1943 under the code name 'Bridge'; the work was completed in April 1944 although the first mustard had arrived on the site in January. It was intended to fill 65lb LC (light case) bombs with liquid mustard vesicant at a rate of one per minute.

Photo:View from the roof of the charging building showing the bonding building (left), toxic change bath house, (centre) and guardhouse/office (right). The roof of the new Anglia Water pumping station can be seen in the background.
Photo by Nick Catford

Two concrete underground tanks or pots (designated J & K) were installed to store the liquid. These tanks were lead lined and oil heated and stored 250 tons of each of the two mustard variants, Runcol HT/Y3 and Pyro HBD/Y25. The pots were each 25 feet in diameter, 25 feet deep, with 18-inch concrete lids. Each had an instrument room to one side. The major buildings on the site comprised storage sheds for empty cases, a bonding building and a charging building where the cases were filled; these buildings were linked together by covered ways. The depot was linked by rail to the London & North Western railway line from Bedford to Cambridge with a junction on the east side of Lords Bridge Station. The short spur ran through the air ammunition park terminating at an external loading dock alongside the bonding building.


Charging building with the water tank on the roof
No munitions were filled at the site after 1945. Throughout the war some tens of kilotons of chemical bombs had been filled and stored and there were still large quantities of bulk mustard gas in store at the forward filling depots. The stocks of the extremely fragile 65lb LC mustard bombs had reached such proportions in March 1945 that a special unit was formed at Melchbourne Park FFD for decanting leaky mustard bombs. Leakers from all the FFD's were sent to this site for disposal.

One airman based at 95 Maintenance Unit remembers destroying piles of mustard gas bombs at Orwell Grange, a satellite of Lords Bridge, by pouring petrol on to the bombs, adding a few incendiaries for good measure and then firing several hundred rounds from a sten gun to start the bombs leaking and ignite the fire. Later the entire pile was covered with copious quantities of bleaching powder.

It was eventually decided to decant agent out of all the 65 lb LC bombs and the spray tanks into storage tanks and dispose of the munitions by incineration followed by dumping. Mustard was decanted out of the pots into three trains carrying five ton road/rail tankers for transport to Randal for filling into 1000 lb aircraft bombs. The first train carried 124 tons and the second 126 tons of either Y3 or Y25 and the third train of 25 tankers presumably holding 5 tons each of Y25

For further information and pictures of Lords Bridge FFD 4 click here

[Source: Nick Catford]

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