Monument record MDO28548 - RAF Portland, Rotor early warning station, Portland

The site of Portland centimetric early warning radar station. It was built between 1950 and 1951 as part of the Rotor programme to modernise the United Kingdom's radar defences and was one of eight examples built across the country. Rotor technical sites comprised radar arrays, a small electrical substation, an operations building and a guardhouse, and were linked by roads and tracks. Portland was equipped with two Type 14 (Mark 8 and 9) plan positioning radar heads, two Type 13 Mark 6 and one Type 13 Mark 7 height finding radar, one Type 54 Mark 3 low-level radar and one AN/FPS3 array for long-range radar. The radar heads were all mounted on plinths or 25 feet gantries apart from the Type 54 radar, which was mounted on a 200 feet tower. Portland featured a non-standard guardhouse designed to resemble a bungalow and built of Portland stone, which gave access via a lift and staircase to a single-storey, underground R1 operations block. The bunker contained the control centre for the Rotor site and was divided into a number of working areas including workshops, radar offices, an intercept recorder and tracking room, domestic facilities, and a plant for air conditioning and gas filtration. The station was non-operational by 1958 and had been reduced to care and maintenance. Surviving surface features at the site include six radar plinths, an emergency exit blockhouse, a communications mast, and the gatehouse.

SY 6957 7335. Site of a Rotor early warning radar station at RAF Portland, built between 1950 and 1951.The Portland site was of the Centimetric Early Warning (CEW) type and was one of eight examples built across the country. The site comprises an irregular enclosure surrounded by fencing with an entrance and guardhouse on the west side. The main guardroom is a single storey, stone-built structure which provided access to an underground bunker. The bunker contained the control centre for the Rotor site, situated on the northern side of the complex, within the outer ditch of the adjacent Verne Citadel. The interior of the bunker was divided into a number of working areas including workshop, radar office, intercept recorder and tracking room. A large reservoir, located in the south eastern area of the compound, provided the original water supply for the control centre. The site also contained seven radar towers, now dismantled. Scheduled. <4>

The Rotor programme was developed to advance the wartime radar technology in detecting and locating fast-flying jets. It was approved by the Air Council in June 1950. The first phase of the programme, Rotor 1, was to technically restore existing Chain Home, centrimetric early warning, Chain Home Extra Low and Ground Controlled Interception stations and put them under the control of RAF Fighter Command. There were three main components to the Rotor stations: the technical site, including the radars, operation blocks and other installations; the domestic site, where personnel were accommodated; and the stand-by set house, a reserve power supply. The technical site of Portland Rotor station was located at SY 696 735. The domestic site and stand-by set house were co-located at SY 682 714.

The two main constructions at Rotor stations were the operations block and guardhouse. Operations blocks were the largest structures built at Rotor stations. They were constructed of reinforced concrete and designed to withstand 2,000lb bombs. The outer walls and roof of the Rotor operations blocks were 3 metres thick and the internal walls between 0.15 to 0.6 metres wide. The exterior was coated with an asphalt damp course and surrounded by a 0.15 metre brick wall. The roof was usually flush with the ground surface and up to 4.34 metres of earth was mounded on top. The operations blocks, identified by a 'R' prefix, contained technical equipment, domestic facilities, workshops and a plant for air conditioning and gas filtration, all within a single complex. The guardhouses were designed to resemble bungalows. They were single-storey buildings capped with a flat, concrete roof, above which a pitched roof contained water tanks. They were generally constructed of brick, but were built to blend in with the local architectural style. The guard rooms also contained an armoury, store, rest room and lavatories. Those associated with underground operations blocks featured a projecting rear annex that housed a stairwell leading down to an access tunnel. <5-6> <8>

Aerial photography from 1996 shows a modern array/tower and attached buildings formerly used for Rotor functions. <7>

Portland Rotor station was constructed in 1950-51 by the contractor Robert McAlpine. The site comprised a non-standard design guardhouse built of Portland stone and an R1 operations block. By 1958 the station had been reduced to care and maintenance and was non-operational. The site was taken over by the United States Air Force, however they did not use the operations bunker, which was damaged by fire in 1969. The site was afterwards used by the Ministry of Defence as a dog training centre. The operations bunker was the deepest Rotor facility, being constructed 70 feet below ground level. It was fitted with a lift surrounded by an iron staircase, rather than the usual staircase from the rear of the guardhouse. Surviving surface features at the site include six radar plinths, an emergency exit blockhouse, a communications mast, gatehouse, kennels, the old United States Air Force compound, and a reservoir built in the 1980s to serve the dockyard. <9>

<1> Council for British Archaeology, 1995, Defence of Britain Project (Digital archive). SWX5.

<2> Council for British Archaeology, 2003, Defence of Britain Project Database (Machine readable data file). SDO128.

<3> Council for British Archaeology, 2006, Defence of Britain Project Archive DEB01 (Excavation archive). SDO17227.

<4> English Heritage, Scheduled Monument Notification, 02-Nov-04 (Scheduling record). SDO17381.

<5> Dobinson, C S, 2000, Twentieth century fortifications in England. Volume XI.1. The Cold War, 36-72 (Monograph). SDO18653.

<6> Dobinson, C S, 2000, Twentieth century fortifications in England. Volume XI.2. The Cold War, 155-156 (Monograph). SDO18654.

<7> Anderton, Michael J, 2000, Twentieth Century Military Recording Project: Cold War Rotor Stations, 45 (Unpublished document). SDO18655.

<8> Cocroft, Wayne D, and Thomas, Roger J C, 2003, Cold War: Building for Nuclear Confrontation 1946-1989, 86-110 (Monograph). SDO18652.

<9> Subterranea Britannica on-line survey (1998-2007) UK ROC and WMO Monitoring Posts, Accessed on 12-JAN-2009 (Digital archive). SDO14745.

<10> National Record of the Historic Environment, 1405267 (Digital archive). SDO14739.

Record last edited

Mar 4 2024 4:43PM