A Thor missile main base established at the former Second World War airfield of RAF North Luffenham, constructed in 1959 and operational until 1963.

The Thor missile main base established at the former Second World War airfield of RAF North Luffenham, constructed in 1959 and operational until 1963, is of national importance for the following principal reasons:

* Period: its intactness and legibility clearly articulates the international historic significance of the Thor sites. They represent one of the tensest periods of the Cold War when their missiles were raised to alert position during the Cuban Missile Crisis of October 1962, an event widely acknowledged to have been the closest yet the world has come to nuclear confrontation. * Rarity: its importance is enhanced by its strong association with a noted example of a late pre-War expansion period aerodrome with significant Second World War interest, and the retention of a Bloodhound Missile Tactical Control Centre - factors which continue to contribute to its interest. At no other British site does the missile base remain within its contemporary military context. * Survival/ condition: the Thor Platforms are the best preserved in the country, their substantially intact survival and archaeological traces allowing the operation of a first generation intermediate range ballistic missile to be understood and communicated. * Potential: the above and below grounds remains have the potential to further contribute to our understanding of the Thor missile operation and its international historic significance. * Diversity: the pillars and other survey markers on and around the Platforms illustrate how the missiles relied implicitly on optical surveying techniques to align their inertial guidance systems on their targets. The search for accuracy is one of the central themes in the history of missile technology and it is aptly demonstrated by the crucial spatial distribution of the emplacements and associated buildings and structures at North Luffenham.

Despite being of national significance, the site is not scheduled for the following principal reason:

* Management considerations: although the monument is clearly of national importance, its Grade II* listed status affords it a high level of protection and the archaeology can be appropriately managed in the planning process under the provisions of the National Planning Policy Framework.

Construction of RAF North Luffenham was completed by late 1940. It was one of a series of stations established under the 1939 M Scheme for expanding the number of RAF airfields. Typically, airfields associated with this programme had two J-type Aircraft Sheds, or hangars, flanking a Watch Office with a meteorological section of 1939 design, with associated technical buildings, domestic accommodation, and open grass flying field. The station opened in January 1941 as Number 17 Elementary Flying Training School. By the summer of 1941, Numbers 61 and 144 Squadrons were brought to North Luffenham from Hemswell, but from 1943 work commenced to lay hard surfaced runways and hardstandings for heavy bombers. The airbase re-opened in March 1944 and was used initially by the Heavy Glider Conversion Unit, but returned to bomber crew training from September of that year until October 1945. In December 1946 the Heavy Glider Conversion Unit returned to the airfield until December 1947 when the airfield passed to Transport Command and 240 Operational Conversion Unit. They stayed until April 1951 when Number 102 Flying Refresher School opened.

With increasing East-West tensions in November 1951 it was decided that the airfield should be handed over to the Royal Canadian Air Force for the deployment of air defence fighters under the country’s obligations to the North Atlantic Treaty Organisation. The Canadians stayed until April 1955 when it passed to RAF Fighter Command before flying ceased in June 1958. Around this time, the airfield was identified as a main base for a Thor intermediate range ballistic missile squadron, and it became fully operational as a Thor base by May 1960.

Many factors were taken into account when selecting the base and satellite stations for Thor. A set of criteria was drawn up and sites surveyed. An important part of the selection process was the site survey. There needed to be sufficient land available at the location which was already in the ownership of the military air force and the airfield itself needed to be suitable for adaption and could accommodate the overlaying of the Thor compound.

Thor missiles were the first operational Intermediate-range Ballistic Missile (IRBM) system deployed by the West during the Cold War. With a range of 1,500 nautical miles, Thor missiles were approximately 20m (65ft) long and 2.5m (8ft) in diameter powered by propellant rocket fuel controlled by two motors. Developed by the United States (US) Government between 1955 -1959, the proposal to deploy Thor in Britain was put before the British Government in 1957. At the time Britain was developing its own IRBM, Blue Streak, which would not be operational for some time. Final agreement to locate Thor in Britain was reached between the Prime Minister, Harold Macmillan, and President Eisenhower at the Bermuda Conference in 1957. The rockets were manned by the RAF who would be trained for the task by the USAF, but the nuclear warheads would remain under US control. Macmillan reported to Parliament that the decision to use Thor against the Communist east would be made jointly by the two countries.

A total of 60 missiles were deployed at 20 sites in the East of England from 1958 under the codename 'Project Emily'. There were four main bases located on pre-war permanent airfields; RAF Feltwell, RAF North Luffenham, RAF Hemswell and RAF Driffield. Although all other Thor sites made use of existing airfields, North Luffenham was exceptional in that additional land was acquired for the Thor launch emplacement complex. At each base an adapted hangar was used to receive the missiles, store the servicing equipment and conduct inspection and maintenance. At RAF North Luffenham, a 'J' type hangar was adapted for this purpose. Usually located on the opposite side of the airfield, the Thor compounds at the main bases had a Surveillance and Inspection Building and a Classified Storage Building, partly surrounded by earthwork banks, where the warheads were inspected and stored. Every main base had four satellite stations, each with their own Squadron. The launch areas at the main and satellite stations were almost identical, with a Classified Storage Building and Pyrotechnic Store placed about 200m away from the nearest emplacement, protected by earthwork banks. The buildings and emplacements lay in an irregularly shaped compound surrounded by a pair of fences. Inside were crew huts, a squadron office and telephone exchange. Close to the main gate was the launch control area, an area of concrete on which the control trailer, generators and an oil tank were placed. The Surveillance and Inspection Building and the Classified Storage Building were under the direct control of the United States Airforce who operated from within an inner, and gated, secure area within the larger secure area that protected each missile complex. With regard to missile delivery, each wing was allocated an ‘airhead’ which would take receipt of the missiles from the US. The airfield at North Luffenham was the designated airhead for the North Luffenham wing.

Exact siting of the missiles was essential to ensure the targets were reached. This was achieved through a specially commissioned survey that saw the 13th Field Survey Squadron Royal Engineers erect two very precisely mapped Trig Points to enable the establishment of a baseline. This baseline was then used to ensure the correct alignment of the launch emplacements. The Thor Trig Points are one of only three sets of Trig Points that do not form part of the Ordnance Survey’s mapping network. In addition to the precise, fixed location of the launch components each emplacement had a theodolite shed and a separate long-range theodolite, set on a concrete pillar surrounded by brass survey points. At the opposite end of the emplacement two short-range theodolites were mounted on a metal platform near to the launcher erector which lay at the centre of each emplacement and was secured to a metal cage set in concrete. Here the missiles, which were stored horizontally on a trailer, were raised to a vertical position. The two fuels which powered the rocket, kerosene and liquid oxygen, were stored in fuel pits on either side of the erector and pumped separately through pipes suspended in concrete conduits. A separate liquid oxygen dump tank was located to the rear of the blast walls in case the fuel needed to be rapidly discharged from the missile. At the far end of each emplacement were two 'L' shaped blast walls.

Thor missiles could be brought to operational readiness in 15 minutes after receiving the authorised and authenticated order to launch. Strict understandings about the operational control of the missile included an agreed British and US launch through a dual key system and a veto for each Government. Although Thor deployment in Britain was an interim measure, their presence played an important part in the Cuban Missile Crisis of October 1962, the most tense period of the Cold War, when fifty nine of the sixty missiles were made ready. Thor was phased out in England between April and August 1963, just short of their anticipated 4 year life-span, North Luffenham being the last site to close.

The missiles remained until they were stood down in August 1963. Concurrently, a Tactical Control Centre with a Type 82 radar was in operation for the control of remotely based Bloodhound air defence missiles. The radar remained in service into the early 1970s as part of the civil air control system. After the withdrawal of the Thor missile squadron the airfield was used by a variety of RAF units. In the 1970s an RAF Regiment Rapier air defence unit was moved to North Luffenham. The RAF remained on the airfield until 1998 when it passed to the army and became known as St George’s Barracks. Since then various army units have been based in the barracks including the Royal Regiment of Fusiliers and the King's Own Royal Border Regiment. From 2007 the 16th Regiment Royal Artillery was housed in the barracks with responsibility for all Rapier missile units. They stayed until about 2014 and were replaced by the Royal Army Medical Corps who remained until 2018. The principal unit on the base in 2020 is the 1 Military Working Dogs Regiment, Royal Army Veterinary Corps. In November 2016 the Government published the document ‘A Better Defence Estate’ in which the closure of St George’s Barracks was announced.

Research and fieldwork on the Thor missile sites was conducted as part of the RCHME ‘Cold War’ project, during which one of the emplacements at North Luffenham was surveyed in 1998, they were later assessed by the Monuments Protection Programme ‘Cold War’ project (2001). The three missile emplacements and the Surveillance and Inspection Building were listed at Grade II* in 2011.

A Thor missile main base established at the former Second World War airfield of RAF North Luffenham, constructed in 1959 and operational until 1963.

PRINCIPAL ELEMENTS: the Thor missile site lies in an isolated position at the extreme south-eastern end of the airfield accessed from the airfield perimeter track. The three launch emplacements are arranged in the typical, broadly triangular configuration within a compound, the inner fence-line of which partially remains to the east, south and south-west of the emplacements. Within the compound are a number of associated features, including the Surveillance and Inspection Building, Ordnance Survey (OS) triangulation pillars, and the remains of demolished buildings and trackways which survive as archaeological features.

DESCRIPTION: the Thor missiles were sited in an irregular oblong-shaped enclave over an area of wartime dispersal points comprising ‘spectacle’ and ‘frying-pan’ shaped hard-standings. Additional concrete tracks were constructed to give access to the missile Platforms or emplacements. The area was surrounded by an 8 ft (2.44m) high unclimbable fence with cranked concrete posts and beyond this an outer perimeter barrier of Dannert wire – coiled barbed wire secured by steel posts. To the south the Dannert wire lay adjacent to the airfield perimeter fence. Internally, at the western end the enclosure was separated by a further fence to restrict access to the Surveillance and Inspection and Classified Storage buildings, which were under US control. The fencing has been removed, but where it crossed existing concrete tracks, and where they survive, traces of fence posts may be found. The enclave was entered from the eastern end of main runway along a newly laid single road, which led to the circular pan of a wartime dispersal point, which was probably retained as a lay-by. Beyond this was the main gate and outside the gate a single Police Car Shelter, just inside was a Fire Tender House (SK 95259 04835) and parallel to the access road to the east a long Guard and Crew Room. No surface traces of these buildings remain. Beyond the main gate the access road followed a wartime taxiway, which has subsequently been reduced to single track width. This in turn gave access to another new single track that led southwards to a roughly triangular–shaped area (SK 95335 04721). This was for the Launch Control Trailer (LCT) area, parked on this were the trailer mounted Power Switchboard and the Launching Control Group, diesel generators and a 5,000 gallon (22,730 litre) oil tank. The track and the surface of the LCT area have been removed, but are marked by a pile of concrete rubble covered in undergrowth. To its north and adjacent to one of the wartime taxiways was the Mechanical and Electrical Building that housed a standby generator, and immediately to its west a bund for a fuel tank which survives as a low concrete wall. To its rear is a cast-iron electrical distribution box by Lucy, Oxford. From a surviving plan it is unclear if there was a direct route to the Surveillance and Inspection building to the west along a wartime perimeter track within the secure perimeter. A standard airfield taxi-way light inserted into the perimeter track at the point where the fence crossed may, however, indicate the position of a gate. The Grade II* listed Thor missile Platforms, or emplacements, are laid out in a roughly triangular pattern, with Platform 1 to the north, Platform 2 to its west and Platform 3 to the south, and are constructed from reinforced concrete to a standard design. At the centre of each was the launcher erector, which was securely fixed to a metal cage set in concrete. Here the missile, which was usually stored horizontally on its trailer under a retractable shed was raised to a vertical position, still on its handling trailer. The kerosene and oxidiser, liquid oxygen (LOX), which fuelled the rocket, were kept apart in tanks to either side of the emplacement to prevent spontaneous combustion. They were conveyed to the rocket along pipes suspended in concrete conduits. Stainless steel fittings indicate the side of the pad used to handle the super-cool liquid oxygen, which has a boiling point of -183 degrees centigrade. A LOX dump tank was provided close to the erector in case the fuel needed to be rapidly discharged from the missile. Other features found on the pads include open channels, originally covered by metal grilles, which carried cabling and pressurised gas pipelines from the support trailers, which in turn stood behind L-shaped concrete blast walls in positions marked by painted lines. Truncated sections of hollow-section steel tubing set into the concrete mark the locations of lamp standards.

The missile’s flight path was controlled by an inertial guidance system that used linked gyro-compasses to detect changes in acceleration as a means of monitoring its precise location, and allowed adjustments to be made to its course. This allowed the weapon to deliver its W-49 (1.44 megaton) warhead to a maximum range of 1,500 miles (2,410km) with an accuracy of two miles (3.2km). For this system to operate efficiently this first generation intermediate range missile needed to be precisely optically aligned before launch. The first stage of this process was to accurately align the launch emplacements and this was achieved by surveying a baseline to locate the survey positions on emplacements. This was done from a line to north about 1354 ft (412m) in length each end of which was marked by a standard Ordnance Survey (OS) triangulation pillar. The pillars were both located in relation to the national grid and North Star. To the north of the emplacements is an intact pillar (SK94836 04746). On the top of this is an integral bronze mounting triangular plate with raised lettering ‘Ordnance Survey Triangulation Pillar’, upon which a theodolite could be set. On the side of the pillar is a bronze Flush Bracket Bench Mark plate identifying it as pillar S9536. Although it was a standard OS pillar, it wasn’t part of the OS triangulation network and the letters OS have been ground down. To the east of the northern pillar is a steel pipe, about 1.2m tall, set into concrete. Mounted on the top of this pipe is a level plate with four holes that might be used to mount an instrument. It is unclear if this was associated with the Thor Platforms. The other end of the baseline is to the south of the former main entrance to the Thor site and is marked by the remains of another pillar (SK95345 04796), which has been broken in two. This also retains its bronze Flush Bracket Bench Mark plate identifying it as pillar S9539; again the OS letters have been ground down. At some distance from the Platforms were tall pillars that supported long-range theodolites. The lower section of one of the pillars survives at Launch Platform 3. Each emplacement was also equipped with an array of survey positions. At the eastern ends of the Platforms were brick Long Range Azimuth Alignment Electro-theodolite houses, whose ruins and foundations may be traced. In the centre of each building was a pillar for mounting a theodolite, and there were large windows through which the missile could be sighted; there was also another theodolite pillar in front of each building. At the opposite end of the emplacement, beyond the blast walls, was a metal platform on which were mounted two short-range theodolites that were centred over brass studs set into the concrete beneath. The cut-off mounting bolts for the platforms and some brass studs remain visible.

All three emplacements retain their blast walls, launcher erector mountings, fuel tank catch pits to either side of the erector, Lox dump pits, and most of the rails on the shelter causeways. The fuel pipe conduits from the pits to the launcher remain and the steel fuel pipes surrounding the launcher mounting are apparent as are the platforms for the short-range theodolites.

Subsequent to the mapping of this area by the Ordnance Survey in 1974 most of the wartime taxiways, dispersal points and some of the new tracks laid for the Thor programme were removed. Although, in some areas satellite imagery shows they remain as archaeological features.

The Thor launch complex has two emergency water tanks, one is located between, and to the south of, the Surveillance and Inspection Building and the Classified Storage Building; the other is midway between the three launch emplacements. They are sunken structures with the top 30 to 40cm rim of the tanks showing above ground level; they are at least 1m deep. Both tanks have been filled with demolition rubble (presumably from other parts of the Thor site) and both are overgrown. To the south of the tank that served the launch emplacements there is an oil trap.

To the north-east of the north emplacement (Platform 1) at approximately NGR 495231, 304808 is a concrete mount, roughly 1.5m square and 10-15cm above ground level, which could have been a mount for a communications mast. The structure was present in 1967 but is not apparent in any pre-1958 aerial images.

The Surveillance and Inspection Building

As described above the western end of the missile area was separated by an internal fence denoting an area under the control of the USAF 99th Munitions Maintenance Squadron which had responsibility for the missiles’ warheads. Within this area were two buildings: the Surveillance and Inspection (S and I) building (listed at Grade II*), where the warheads were checked before issue and minor maintenance work was carried out, and the two-bay Classified Storage building, which could be used to hold two warheads on their handling trolleys. The Classified Storage building and its protective bank were demolished sometime between 2000 and 2006, although its footings are still visible. A 20,000 gallon storage tank sited in this area was not visible during the site inspection (July 2020) due to being overgrown but it does remain. The circular 78.000 litre Emergency Water Supply (EWS) tank is modern.

The Surveillance and Inspection building (SK 94675 04389) has a rectangular ground plan and is orientated roughly north to south. It is split level with, to the west, a single-storey, cement rendered brick bay with a flat concrete roof. This was probably the plant room for the building. In its western elevation is a double door, a wide roller shutter door, a personnel door and a blocked personnel door. In its northern elevation is a double door. To the east is a two-storey bay. Elsewhere these sections were steel-framed with prefabricated concrete panel cladding. This section is entered through a roller door in its northern elevation and has been reclad in pressed metal sheeting. The interior was not inspected. Originally this was protected by an earthen bank to the east and west. This has been reconfigured and is now U-shaped in plan, with a shorter arm to the west, and lies across the original entry track to the south side of the building.

AREA OF NATIONAL IMPORTANCE

The area of national importance is defined by the line of the unclimbable fence shown on the 1963 site plan. This surrounds the three launch emplacements, the trig point to the north and the Surveillance and Inspection Building to the west. Archaeological remains of national importance may lie outside this area.