M72 East Cliff Coastal Defence/Chain Home Low Radar Station, Portland, Dorset

Summary

Second World War Coastal Defence/Chain Home Low Station M72 East Cliff on Portland, operational between 1941 and 1942. Two buildings, situated on an exposed limestone cliff which drops off dramatically to the sea.

Description

MATERIALS: Both blocks are of red brick with concrete lintels and roof. The power-house has a reinforced concrete element to the southern end.

PLAN: A rectangular transmitter and receiver block (TXRX) and to its west an irregular T-shaped stand-by power-house.

TRANSMITTER AND RECEIVER BLOCK (TXRX): Located close to the cliff edge in an exposed position roughly orientated north-south.

EXTERIOR
A rectangular single storey building approximately 3m high with two straight brick piers to the east and west elevations. Its flat concrete roof extends beyond the external walls and fragments of its bituminous waterproof membrane remain. Doorways are located on the east and south elevations; no doors are retained but the metal frames from the former blast doors survive. There are four window openings in the east, one in the north, one in the south and two in the west elevations. All windows are standard size and have had modern mesh inserted. They all retain their internal shutter brackets, but no original blast shutters remain. The window to the east elevation retains its metal window frame. Small regularly-spaced rectangular ventilation openings are located on the north, east and south elevations. No remains of the metal plates that would have supported a rooftop gantry and aerial array are thought to survive but there is evidence of the transmission of power from the room below to the roof, evidenced by circular holes that would have housed the turning mechanism for the transmission.

INTERIOR
The building comprises three rooms; two small end rooms flanking a larger central plotting room. The end rooms are linked to the plotting room by doorways. No doors survive but fragments of the sliding mechanism remain. Remains of interior paintwork survive in the plotting room and fragments in the end rooms. The ceiling is bare concrete. There are no fixtures and fittings but some witness marks show where the cable ducting positions and equipment was positioned. Evidence of the power transmission remains to the roof in the form of a small brick chimney encasing a ceramic pipe that would have housed the turning mechanism for this transmission. Metal brackets between walls and ceiling remain in the corner of each room.

STAND BY SET HOUSE (POWER-HOUSE): Located approximately 20m to the north-west of the transmitter and receiver block and partially subterranean.

EXTERIOR
A single-storey irregular shaped building with no windows standing approximately 3m tall with concrete roof that slightly extends the external walls. There are small regularly-spaced rectangular ventilation openings located on the north-east and west elevations. The southern end has a concrete wraparound porch feature with three access points and an additional open shelter.

INTERIOR
The building has one main internal space with a wrap-around porch to the south that provides three access points, all open.

There is also an open shelter attached to the southern side, possibly a fuel store.

History

The introduction of the aircraft as an offensive weapon provided the rationale for strategic air defence systems adopted by Britain from the early 1920s. These systems initially involved early warning, based on the visual spotting and tracking of aircraft, but developed through acoustic detection devices to radar. The principles behind radar were widely recognised by the 1930s, but British technicians were the first to translate the science - that an electromagnetic pulse reflected from an object betrays that objects position to a receiver - into a practical means of defence. Following experimental work at Orfordness and Bawdsey Research Station in Suffolk, radar developed through the initial Home Chain, a small group of stations in the extreme south-east of the country, to Chain Home Low (CHL) stations which filled gaps in low-looking cover left by the original technology. A further addition in 1941 was Coastal Defence/Chain Home Low (CD/CHL), a low-cover coastal radar designed to detect surface shipping and low-level aircraft.

Radar stations were designed for raid reporting, passing information to a central operations room which in turn directed fighters to intercept enemy aircraft. This system was to prove vital during the Battle of Britain. Radar was constantly evolving and played a significant role in alerting and deploying night fighters during the Blitz of 1940-1941. Range and accuracy improved during the war and aided Fighter Command in their offensive sweeps over occupied Europe from 1943. Many radar stations were reused during the Cold War period for Rotor, a later development of wartime radar.

The Coastal Defence/Chain Home Low Station named M72 is located on East Cliff in Portland, close to the cliff. The station would have been one of two such stations on Portland, the other being M73 West Cliff (now demolished) both under the British Army’s control. It is understood that M72 East Cliff was operational by mid-1941 and ceased operation in November 1942, following the opening of the Chain Home Extra Low (CHEL) station K73 within the nearby Verne Citadel.

M72 East Cliff is a Type`M' radar station established in 1941 as part of the national coastal defence Chain Home Low (CD/CHL) system. The M pre-fix relates to them operating with a 1.5m radar.

M72 East Cliff comprised of a transmitter and receiver (TXRX) block with aerial array located on a metal gantry set on the roof and a stand-by power-house, to provide an emergency power supply to the transmitter/receiver block. It is understood that in some locations accommodation and service buildings (Nissen huts) were situated close to these stations. No evidence survives to indicate that this was the case with M72. This may have been because of its proximity to the Verne Citadel, where ample accommodation and service buildings would have already existed. It is likely that the site would have been powered by a mains electricity supply, which in this case might have been provided from the Verne via underground cables. Documentary evidence from November 1941 shows that at that time one platoon was stationed at East Cliff, and another at its sister station West Cliff.

Reasons for Listing

M72 East Cliff Second World War Coastal Defence/Chain Home Low Station, on Portland, is listed at Grade II for the following principal reasons:

Architectural Interest:
* M72 East Cliff is a substantially intact coastal defence/chain home low radar station that retains its two principal buildings which provide a clear understanding of how the site functioned;
* the buildings at the site are the full extent of the original station at East Cliff and retain their external form, including plan-forms with room functions clearly legible. Despite the loss of some fittings, internal features such as cable ducting and witness marks on the walls on the TXRX building do survive, making them a rare surviving example of their type.

Historic Interest:
* M72 East Cliff is an example of the Coastal Defence Chain Home Low stations that were an important phase of radar development during the Second World War;
* the site represents a physical manifestation of war-time tensions and fears, and the need for a national defence system which resulted in the construction of a chain of radar stations to protect Britain’s coast.

Group Value:
* M72 East Cliff has a strong group value with the many other listed buildings and scheduled monuments associated with Portland’s military heritage, including Portland's fire command post located at East Weare Camp (Grade II) and the successor station, K73, which was established within the Verne Citadel (a scheduled monument);
* the station would also have supported the Army's range of coastal defences in operation during the war including East Weare Battery (Grade II), the Breakwater Fort (Grade II), Nothe Fort (scheduled monument and Grade II*) and the Upton Battery (scheduled monument). East Cliff also has links to the nearby RAF Ringstead Chain Home radar station (Grade II).

External Links

Historic England Listing

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