Monument record TR 34 NE 420 - St Margaret's early warning radar station, Throwley, Swale

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 for St Margaret's radar station was located at TR 370 451. The dometic site and stand-by set house were co-located at TR 356 444.

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. (1-3)

Aerial photography from 1979 shows that no surface features of the radar station survive, only Second World War buildings. However, the tunnels below the site within the cliff are likely to be the only surviving features of the station. Partial structural remains surviving as earthworks at TR 366 452 may contain secondary access or escape exits to these tunnels. (4)

St Margaret's Rotor station was built in the early 1950s and closed in 1960, although it was kept on care and maintenance until 1981. In 1982 the underground operations bunker was sealed off and all surface features demolished apart from the guardhouse, which has since been refurbished for private habitation. (5)

<1> Cocroft, Wayne D; Thomas, Roger J C, 2003, Cold War: Building for Nuclear Confrontation 1946-1989 (Bibliographic reference). SKE58760.

<2> C.S. Dobinson, 2000, Twentieth century fortifications in England. Volume XI.1. The Cold War (text) (Bibliographic reference). SKE58761.

<3> C.S. Dobinson, 2000, Twentieth century fortifications in England. Volume XI.2. The Cold War (Appendices) (Bibliographic reference). SKE58762.

<4> Michael J. Anderton, 2000, Twentieth Century Military Recording Project: Cold War Rotor Stations (Bibliographic reference). SKE58763.

<5> Peter Higginbotham, 2000, The Workhouse (Website). SKE56079.