Monument record 0942000000 - Signal Hill Transmitter Station

World War II radio transmitter station used for Foreign Office broadcasts. Site recorded for Defence of Britain project, included a brick transmitter building, built by a local contractor. Condition recorded as good during field visits in September and November 1996 (B1).
After war, thought to be used as an MI6 Signals Intelligence (SIGINT) site, possibly a 'Numbers Station' transmitting encoded shortwave messages to MI6 agents (B2).
Radio masts dismantled after October 1988 (visible on BCC vertical AP) and before 1999 (B3).
Harold Robin was asked in 1940 to find a suitable site to build a shortwave radio station to transmitt propaganda in German and he chose a large field at Gawcott. Approached by a gravel path and a four-foot high barbed wire fence surrounded the site. Personnel were accomodated at lodgings in the village. Initially one transmitter was accomodated at the site, called Geranium, housed in a wooden building. A second transmitter, called Gardenia, was bought in December 1941 and when it arrived it was housed in a brick building 350 yards from the wooden one. Both buildings were surrounded by brick built blast walls. Midway between was a small brick structure where the telephone line terminated. This was also an office for the officer on site. Next to each transmitter was a brick built powerhouse, each containing a diesel powered generator. Pre-recorded broadcasts on glass discs were brought every day from the studios at Whaddon Hall and later Wavendon Towers until Geranium was linked by landline to another studio and the work involved monitoring the broadcast. Gardenia started transmitting morse in late 1944 to S.H.A.E.F, the special operatives executive, using the telephone lines. After the war the radio station was expanded and remained in Government use until recently. Today the site accommodates a number of small businesses (B4,B6).

A Second World War and Cold War military transmitter station is visible on historic aerial photographs and was mapped as part of the North Buckinghamshire Aerial Investigation and Mapping project (EBC18304). Located on Signal Hill on the road between Lenborough and Gawcott and centred at SP 69170 31905, the site is accessed by a trackway from the road that leads to two clusters of buildings, each surrounded by an irregularly shaped enclosure of barbed wire. A rectangular building about 16 x 6.5 metres is surrounded by a blast wall, contained within which would have been an American built transmitter. Some 35 metres to the NE is a rectangular building about 11 x 4.3 metres that would have housed the diesel generator. Centred some 190 metres to the E is a second barbed wire enclosure, within which there are two buildings and a turning circle for vehicles. The 16 x 9 metres rectangular building held the second American built transmitter. Adjacent to this are tow further rectangular buildings, 10 x 5 metres and 8 x 5 metres, one which was the diesel generator house and the other an office. Midway between both enclosures is a small 3.5 x 2 metres rectangular structure in which terminated the telephone line. To the south of the barbed wire enclosures are 8 masts, set out in 2 parallel rows. Each row of 4 is separated by about 54 metres and each mast within a row is about 58 metres apart. Other smaller masts are scattered around the site. After the war, the station continued in use and became a MI6 SIGINT station.

On aerial photographs taken in 1961, the west-most transmitter building and its surrounding blast wall has been demolished, as have the barbed wire enclosure and part of the access trackway, which has been re-routed. All the masts have also been demolished. In the east-most enclosure, the office is demolished and the site’s security fence has been re-routed. Also, a semi-circular building with a radius of 12 metres has been constructed adjoining the wartime transmitter building. The station was closed in the late 1990s. By 2003 the generator in the west enclosure has been demolished, as has the small telephone line structure between the enclosures. Between 2004 and 2007 the transmitter building and generator building in the east enclosure are demolished and other buildings are then constructed in their place. All that remains of the original wartime constructions is part of the original access track leading from Lenborough Road.

Probably in the mid-1960s a large X-shaped telecommunications structure was constructed to the southwest of the site, centred at SP 69028 31818, comprising four arms each of 50 metres long and 5 metres wide, protected by a surrounding post and wire fence. In the centre of the X is a large mast, with each arm having a smaller mast located within it about 5 metres in from the distal end. On the W and E facing sides, a linear N-S aligned 68 metres long fence joins the ends of each two opposing arms, with each fence having a 4 metres gap in the N end. The X structure remained extant in 1990 but appears entirely demolished by 2003. Recent remote sensing data shows the X shape of the structures clearly visible cutting through the medieval ridge and furrow cultivation earthworks.

The site is now called Signal Hill and used for industrial purposes by various companies (7-12).