Scheduled Ancient Monument: Anti-aircraft site at Searson's Farm, Trimley St Mary (1420538)

Summary of Monument A Cold War heavy anti-aircraft gun site comprising four gun emplacements, a generator and gun store building, a Command post and partly ruinous radar tower, and a telephone test hut, constructed in 1946. Reasons for Designation The anti-aircraft battery at Searson’s Farm, Trimley St Mary, constructed in 1946, is scheduled for the following principal reasons: * Survival: the site retains most of the key components of the Cold War ensemble including the gun emplacements, generator building, gun store and Command Post, and some of original mountings and fittings; * Historic importance: is an important and evocative witness to the nation’s cultural, economic and military experience during the Cold War, demonstrating the importance of air defence, and its rapid technological enhancement, during the C20; * Rarity: the ensemble is a rare example of a 5.25 inch calibre battery surviving to such an extent, and retains a ramped, brick radar tower, considered to be a very rare survival indeed; * Group value: it has historical and functional group value with the Anti-Aircraft Operations Room at Furze Hill, Mistley, which controlled the Searson’s Farm battery and all of the anti-aircraft sites in the Harwich area, and is listed at Grade II (National Heritage List 1391976). History After the end of World War II, 210 anti-aircraft sites were retained to form the core of any future expansion of the country’s air defences. By 1950 a total of 78 sites, 54 of which had permanently mounted guns, were operational in three main areas of defence; the Forth/Clyde, Mersey/Midlands and London/south-east. With the outbreak of the Korean War, and fears that an attack on Western Europe may ensue, Britain’s air defences were strengthened considerably. By April 1951, 684 positions were planned comprising the existing sites, rehabilitated sites from the War and newly built defences. The army had responsibility for anti-aircraft defences which were divided into 33 gun-defended areas. Within each area, guns were commanded from an anti-aircraft operations room (AAOR) staffed by army personnel in purpose-built reinforced concrete, partly subterranean bunkers from which information was passed to the individual gun sites. At each gun site there were between two and eight heavy anti-aircraft guns of either 3.7 or 5.25 inch calibres, each with their own distinctive site plan. The site at Searson’s Farm is typical of a late WWII or early post-war 5.25 calibre design, of roughly square plan with a gun emplacement on a spur at each corner. The Historic Environment Record (HER) for Suffolk records that it was built in 1946 near to the site of a WWII battery. Aerial photographs of the 1940s show a command post at the centre of the emplacements (no longer visible) and a road (a farm track in 2013) leading south-eastwards to the domestic site (no longer surviving) which comprised a number of temporary accommodation buildings, concrete roads and paths. A trench air raid shelter and single gun sites were located nearby, but these are no longer apparent. A generator building, erected at the site to supply electrical and hydraulic power to the emplacements, remains with a gun store attached. The Command post lies 160m further south on the east side of the track; adjacent is a partly ruinous, tall brick tower with an access ramp, on which the radar was raised. After the election of Churchill’s Conservative government in October 1951, it became clear that the economy could no longer support extensive air defence of this type. Developments in aircraft design resulted in high-altitude bombers armed with hydrogen bombs which could carry unstoppable missiles rendering traditional anti-aircraft gun emplacements nearly obsolete. In March 1955, Anti-Aircraft Command was disbanded and the gun sites were dismantled and abandoned. The gun site at Searson’s Farm is surrounded by agricultural cultivation, but the main track to the emplacements, the generator and gun store building and Command post remain. Details PRINCIPAL ELEMENTS The monument lies near to the mouth of the Orwell river, on a plateau to the north-west of the port of Felixstowe, and includes the structural remains of a Cold War heavy anti-aircraft site comprising four gun emplacements and associated buildings; the former generator and gun store building, Command post and partly ruinous brick radar tower, and a telephone test hut. DESCRIPTION The four gun emplacements are located on concrete spurs which extend from the corners of a roughly square concrete platform measuring 40m east-west and 50m north-south located at TM27643615. The centre of the platform is covered with dumped material. Each circular gun emplacement is approximately 10m in diameter and constructed of reinforced concrete. Although two of the four emplacements are heavily covered with vegetation, all appear to survive well, with a central gun pit approximately 1.5m deep to accommodate the traversing mechanism of the gun and hydraulics of the automatic loading system. Attached to the rear of each gun pit is an engine house which contained a diesel generator, hydraulic pumps and an air compressor to power the recoil system. None of the equipment, mechanisms or pipe work appears to survive. Approximately 45m to the south-east of the emplacements, on the west side of the track, is the generator house and gun store, a single storey, flat-roofed, reinforced-concrete, L-shaped building with heavy steel-shuttered doors and windows. At the southern end of the building, the gun store has small square apertures near to roof level and steel-louvre ventilation openings. No interior inspection was made. Opposite the generator house, approximately 20m eastwards from the east side of the track, is the telephone test hut, a brick and reinforced concrete structure with a flat roof. Approximately 160m further to the south of the generator house and gun store on the east side of the track lies the Command post, a flat-roofed, reinforced-concrete structure with a steel-shuttered door. To its north-west lie the remains of the brick radar tower and ramp. No interior inspection was made. EXTENT OF SCHEDULING The monument includes the gun emplacements, generator building, gun store, command post, radar tower and telephone test hut. The position of the telephone test hut on the map is indicative only. The trackway, although contemporary, is excluded from the scheduling.