Atomic Weapons Research Establishment Foulness Island, 1947 Explosives Storage Area


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:
Statutory Address:
Former Ministry of Defence Nuclear Weapons Testing Centre, Foulness Island , Essex


Ordnance survey map of Atomic Weapons Research Establishment Foulness Island, 1947 Explosives Storage Area
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Statutory Address:
Former Ministry of Defence Nuclear Weapons Testing Centre, Foulness Island , Essex

The building or site itself may lie within the boundary of more than one authority.

Rochford (District Authority)
National Grid Reference:


The 11 buildings and infrastructure of the former Explosives Storage Area of the Atomic Weapons Research Establishment, Foulness Island, Essex, established in 1947.

Reasons for Designation

The 1947 Explosives Storage Area on Foulness Island is scheduled for the following principal reasons. * Historic importance: the site is nationally and internationally important through its association with key historical figures and events connected to the development of Britain’s first nuclear bomb; * Rarity: the earliest 9 buildings in the Explosives Storage Area demonstrate innovative technologies and are unique nationally and internationally; * Diversity: the site has a high diversity of component buildings and structures including the distinctive oval infrastructure which practically and functionally linked the buildings, and therefore the processes which took place within them; * Survival: the buildings and structures survive well, the alterations reflecting the evolution of the site; * Documentation: the site is well documented and researched, underpinning the assessment of national importance.


Located at the south-east tip of England, Foulness was first mentioned in the late C12; the name is probably derived from the old English 'Fugla-næss' meaning wild birds’ headland. It is the largest of a number of islands clustering off this part of the Essex coast, characterised by numerous meandering creeks and extensive tracts of saltmarsh, historically used for sheep grazing. Throughout the medieval period, Foulness provided valuable marshland grazing for flocks of sheep in turn supplying, milk, butter, cheese, wool, fleeces and meat. The coastline was also a valuable inshore fishery and oyster beds were developed on some of the creeks. During the post-medieval period the emphasis moved towards arable cultivation and the supply of wheat for the London market. By 1840, settlement pattern of the area later occupied by the Atomic Weapons Research Establishment was a mixture of small farm complexes and scattered cottages. Until the early C20, this remote island was accessible only by boat from the Rivers Crouch and Roach to the north, or an intertidal trackway across the Maplin Sands from the south known as 'The Broom Way' after the withies which marked its route. The acquisition of the island by the War Office during World War I prompted the construction of a permanent land road, Foulness Road, completed in 1922. During both World Wars it seems that the island was used for storage and ad hoc weapons testing. During World War II, numerous temporary hutting, accommodation, roads and operational structures were constructed on Foulness, including the Atlantic Wall, a stretch of reinforced concrete wall built purposefully to practice breaching German defence lines before the D-Day landings. The land later used by the Atomic Weapons Research Establishment (AWRE) was occupied by the Armaments Research Department (ARD) which acquired a further 420 hectares immediately post-war to consolidate all of its detonation programme on the island. The ARD's new Shelford Range was surveyed in 1945 and the land was cleared of all previous structures before the new facilities were constructed. The earliest structures relating to the development of Britain's first nuclear bomb at Foulness comprised a headquarters complex and the Explosives Storage Area.

On 8 January 1947, within the Attlee government a small secret cabinet committee, known as Gen 163, took the decision that Britain should proceed with the development of the atomic bomb. The team put in charge of developing Britain’s atomic bomb was led by William Penney, Chief Superintendent Armaments Research (CSAR), a physicist and a leading member of the wartime British Mission to the United States Manhattan Project that was responsible for creating the first atomic bombs. Penney had played a prominent role in the project, in addition to his scientific contributions, he also sat on the Target Committee, which discussed which Japanese cities should be attacked, and flew with the mission that dropped the bomb on Nagasaki to film its results. It wasn’t until May 1947 that Penney was appointed to lead the British bomb project, responsibility for which was given to a specially created division of the ARD. To disguise its real function it was called Basic High Explosive Research (BHER), its title usually abbreviated to HER, which functioned as a secretive and autonomous section of the larger organisation. Initially, the team comprised 34 ARD scientists, a figure that quickly grew to a few hundred. Initially, its main activities were split between Fort Halstead, Kent and the Royal Arsenal, Woolwich.

During June 1947 this team drew up the development plan for the production of a British atomic bomb. It was during this initial planning period that Shelford Range was transferred to the High Explosives Research (HER) project. Within the atomic bomb project the HER team initially had responsibility for designing and producing the high explosive lenses, the development of the electronics needed to detonate the bomb, and the construction of the precision metal casing that would hold all the components together. The original layout of the Explosives Storage Area, similar to those in an explosives filling factory, whereby explosives and other components manufactured elsewhere were brought together for assembly, comprised an oval enclosure with a concrete track on the inside, its central axis oriented north to south. A plan dated December 1947 shows the track and 9 explosive storage and handling buildings on next to it in the southern half; a further two security buildings flanking the entrance at the south-west corner are not shown on the plan, but are believed to be contemporary. The oval was enclosed by a fence which was removed during the later expansion of the site presumably. In late 1947 modifications to the original plans meant the specifications for some buildings in the Explosives Storage Area took place, including increasing the size of the Explosives Preparation Laboratory (known as X6 and formerly building 23), and its size was quadrupled from 7600 cu ft (215 cu m) to 34,974 cu ft (990 cu m). This implies that at a relatively early stage in the project, Foulness was identified as the place of assembly for Britain’s first atomic bomb. The width of the main door opening, and the RSJ with a 6 ton pulley block, indicates that they were working on the assumption that the device would be comparable to the Fat Man physics package. To test the assembly procedures, a mock-up weapon comprising concrete lenses, known as Alfred, was assembled in X6. Ernest Mott and his team in the explosives section at the Royal Arsenal, Woolwich, produced the high explosives lenses. During the initial design stages lenses were sent across to Foulness for test firing, and as work progressed more and more lenses were joined together for test firing. In April 1949 a six unit trial was staged - the whole bomb comprising 40 separate hexagons and pentagons of high explosive. Later a whole hemisphere, representing over 2 tons of explosives, was assembled and fired.

In the early 1950s the Explosives Storage Area was expanded, and in 1952, played a central role in Britain’s first atomic bomb tests, codenamed Hurricane. The components for the bombs were brought together for assembly at Foulness from the principal manufacturers: the Royal Ordnance Factory at Chorley in Lancashire, Fort Halstead and Chatham Dockyard in Kent, the Royal Arsenal, Woolwich, and the Percival Aircraft Company, Luton. Ernest Mott and George Gallie from Woolwich led the assembly team, which included H S Weeks and a group of technicians, including Mr Hessen who was in charge of metrology. X6 was used for the assembly work; these preparations culminated in the summer of 1952 in the assembly of the high explosive elements for the Hurricane test that resulted in the successful detonation of Britain’s first atomic device. Recent research has revealed that up to three live devices, Hero, Hengist and Horsa, were prepared, the latter two named after two semi-legendary early C5 Jutish warrior brothers, who along with their war band were invited to defend Kent from the Germanic tribes.

On Thursday 5 June 1952 one or more of the devices were taken by lorry to Shoeburyness and then by barge to a war surplus river class frigate HMS Plym moored at Stangate Creek, Sheerness, Kent. ‘HMS Plym’ was then escorted by the trials flag ship 'HMS Campania' on her eight week voyage to the test site, the Monte Bello Islands off the northwest coast of Australia. After their arrival a further eight weeks were spent erecting the structures and equipment that were to be subjected to the full force of the device and preparing the firing circuits and monitoring equipment. The fissile core for the device to be used in the trial was flown to Australia by Sunderland flying boat - it arrived on 18 September. A device was successfully detonated on Friday 3 October 1952 producing an estimated yield of 25 kilotons, 4 kilotons greater than the similar bomb dropped on Nagasaki in August 1945. Some of the personalities that may be linked with Foulness and the overseas trials include the most senior officials William Penney and Roy Pilgrim. Amongst the known Foulness scientists N S Thumpston, an expert on blast effects, was present at the 1956 Buffalo series of trials. Edward Drake Seager, a War Office employee co-ordinated the target response tests and worked closely with Foulness staff on these and later trials. This series of tests at Maralinga Field, Australia, included the first airdrop of a British atomic bomb, weapon effects tests on a variety of structures, military equipment and aircraft, and the indoctrination of large numbers of military officers into the realities of nuclear war.

The Explosive Storage Area was rapidly expanded in a building campaign after the 1953 floods.


The Explosives Storage Area lies towards the northern end of the AWRE site in an enclosed compound to the north of a major drain. The scheduled area comprises the infrastructure servicing 11 explosives storage and security buildings constructed between 1947 and February 1953. The buildings are built of yellow stock brick, with flat reinforced concrete walls, and arranged mostly around the southern half of the oval of 1947. The entrance to the track is located at the south-west, flanked by two buildings: X25, a store room of two building phases which may also have been used as a search room; and XPP2, a police lodge. All the explosives related buildings in the area are protected by two single or a pair of lightning conductors, a method of protecting explosives buildings which became standard practice from the 1940s but was used from the outset at Foulness.

The key building in the group is the Explosives Preparation Laboratory X6 (23), where the explosives components of the devices for the Hurricane trials were assembled. Located approximately half-way up on the west side of the oval, X6 is a split level, flat-roofed rectangular building divided into two sections; a taller (6.04m) assembly bay to the north and a lower (3.19m) metrology and changing room bay to the south. The south elevation has three, 12-light, metal Crittall windows with concrete lintels and brick sills, all protected by metal shutters and there are two similar windows in the west elevation lighting the metrology room. A single, copper-clad door and one, 21-light window is at the north elevation of the assembly room. The assembly bay was entered from the west though tall sliding doors, replaced in the later C20. The southern bay is entered through a copper sheet-clad door at the southern end. Internally, the assembly room has an RSJ with a 6-ton pulley block, capable of lifting a device comparable in scale to the Fat Man bomb. Personnel entered the building through a single copper-clad door at its southern end. This led into a changing area typical of any building associated with handling explosives. On entering is a ‘dirty area’ where outdoor shoes were placed in the shoe boxes and if necessary, clothing changed. The personnel then stepped over the toe board, separating the dirty from the ‘clean area’ and put on the regulation magazine shoes. At the eastern end of this room were wash basins and an office, and to the north were doors into Laboratories 1 and 2. The relatively wide central door opening measuring 6ft (1.83m) between the main assembly room, Laboratory 1, and Laboratory 2 may suggest that some assembly work was done in this room. Laboratory 3 was used in later years as the metrology room, used for the precise measuring of components prior to assembly, and there is a large and heavy steel table at its centre. It is known that Mr Hessen was in charge of the metrology in 1952 and it is presumed that Laboratory 3 had this function at that date.

X6 played an important role in the development of the explosive lenses. Technically the manufacture of the lenses was extremely challenging, each of the lenses comprised alternate layers of cast high and low explosives. These had to be produced to very fine tolerances and free from any internal cracking that might develop during cooling. The explosive element of each lens was held in an outer aluminium shell, these were then joined together to form the bomb. The precision of this assembly work was absolutely critical to the operation of the bomb, as any misalignment of the lenses might result in the misdirection of the explosive shock wave on the fissile core. The basic principles were known from the wartime Manhattan Project. It was, however, an entirely new process to the British team tasked with the production of lenses. To approve this novel design and to gain experience, work at first concentrated on assembling a few lenses for test firing on the ranges, but tested further in the inert device, Alfred (see history above). It is likely that all three live devices were assembled in X6, but were unlikely to all have been kept there and may have been stored in X20 on the north-east side of the oval (see below).

To the west of X6 is the Non Explosives Components Store X5 (23a), its function is self-explanatory and supported the activities in X6. It is a single-storey, yellow stock brick building with flat concrete roof surmounted by lightning conductors, and lit by small, metal Crittall windows with concrete lintels and brick sills, all originally protected by metal shutters. The building is entered through a narrow door at the east elevation. When the lenses for the bomb were delivered from Woolwich they might either be taken directly to X6 or held in store. Buildings that may have been used to store the lenses include the Bare Charge store X21 (19); a contemporary footpath leading directly to X6 suggests a functional relationship between these buildings. X21 is a single-storey rectangular building with a flat roof, protected by copper strapping and lightning conductor poles In the east elevation is a projecting entrance porch with a metal door and a block opening in its south elevation. There are blocked elevations in the south and north elevations and a brick electrical isolation switch locker to the north. To the north of X21 is X20 (17), a high explosive store, a 5 bay rectangular, single-storey building in yellow stock brick with a thick, flat concrete roof supported on RSJ's. Full-height sliding metal doors lie at the east elevation and the south elevation has 18-light metal Crittall windows with hoods, five at the north and south elevations. The building is protected by copper strapping and lightning conductors. Internally, the overhead lifting beam and formerly open interior appear to be of sufficient size to have handled and accommodated at least two devices.

In addition to work on the development of the bomb another priority during the late 1940s was the understanding of blast effect on buildings to assist in civil defence planning. During the Second World War considerable knowledge on the effects of blast had been built up by studying bomb damage on different British building types and, immediately after the war, by visits to Germany and Japan. By 1947, some consideration was being given by the Fort Halstead team to the use of balls of high explosives to simulate the effects of an atomic air burst. To support this work specially shaped charges of high explosives were required to simulate the blast waves produced by larger explosions, the results of which could be mathematically scaled up to model the effect of an atomic weapon. It was probably to support this work that the Explosives Casting and Pressing Laboratories X23 (29) were also specified in late 1947. This building is entered from the south through double copper-clad doors into a lobby area, which also gives access to the Motor and Boiler House. Personnel entering the building were required to change into magazine shoes and clothing before passing over a barrier into the ‘clean area’. Explosives, presumably in sealed containers, were also brought into the building through the main doors suspended from the L-shaped RSJ lifting beam, rated at 1 ton. Once in the Explosive Preparation Room they were presumably unpacked before being taken to the Casting Room or one of the press rooms. Along the northern side of the building are three press rooms and a Compressor Room, where the hydraulic pressure for the adjacent rooms was produced. Due to the hazardous nature of the activities the main spine wall separating the press rooms from the central corridor is formed of 14 inch (0.36m) thick reinforced concrete. The fly press and 200 ton press specified in December 1947 remain in place, along with a compressor and 1 ton lifting beam. At a later date, to improve the building’s operational safety a number of doors were inserted in its outer walls. An early modification to the building appears to be a set of tall, copper-clad doors giving access to the 200 ton press room and linking it directly by a cleanway to the Powder Store X23A (18), to the north, a small rectangular building aired by metal ventilation grilles. A cleanway was also constructed around the western and northern sides of the buildings, and three doors inserted into its west wall. On the northern side a door was inserted to give access to the compressor room and the internal access to this room blocked. The south elevation of the small, rectangular Building X3 (22) to the west, described as a ‘Store for munitions which may not be stored in other explosives stores’ and was also referred to as a Special Store, may also have been used for this function. To the west of X23 are the Detonator Store X24 (20) and Magazine X4 (21), both small rectangular buildings with copper-clad doors, external electrical isolation boxes and flat, reinforced concrete roofs.

The scheduled area includes the concrete road and paths laid out in accordance with the plan of 1947, the buildings itemised above and lamp posts constructed between 1947 and February 1953. It excludes the buildings, structures, fences, fence posts and infrastructure which post-date this period and the central area of the oval track, including the pond to the north of the footpath that links buildings X6 and X21.


The Atomic Weapons Establishment, Foulness, Essex: Cold War Research and Development Site, Survey Report.
English Heritage: Cocroft, W D and Newsome, S. 2009,


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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