The Radio Mast
During 1967 the Government Communications Headquarters (GCHQ) set up an experimental radio and monitoring station.
Blakehill's radio mast was a well known landmark for people of Cricklade and nearby Purton. It claimed to be one of the UK's tallest wooden structures at 240 feet and was known to have a Peregrine Falcon nesting at its very top. This was one of many other top secret instruments that were set up during this period, and although we know of some projects, much is still either secret or difficult to research at this time.
No secret was made of the sites use at the original airfield main gate - they put up a sign to help you. However the security was tight, with armed patrols being carried out and the use of dogs and deadly force authorised, as would have been the norm for any MOD site.
It is believed that the site was experimenting with OTHR, and during the early 70's it was monitoring the weather conditions in the north Atlantic. It was also the first location in the UK to hear of the Argentine invasion of the Falkland Islands.
Unofficially, the instruments at Blakehill were also listening to communications from the Eastern Bloc countries.
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It is thought that the mast was a re-purposed (or surplus, but this is unlikely) tower from the east cost "Chain Home" radar system that was set up in the 1940's. The towers were made of wood to "avoid influencing the balance and symmetry of the receiver dipole stacks by the proximity of any metallic parts"
(source http://www.geograph.org.uk/article/RAF-Stoke-Holy-Cross-Chain-Home-radar-station)
What we can say for sure is that Blakehill's Cold War role ended with a crash on Wednesday 26th January 2000, when as part of the site's decommissioning the mast was demolished along with the support buildings. Nothing remains of the monitoring equipment today, other than mounds of vegetation where the mast once stood and a crop mark - see photo.
One lone piece of the radio mast is on display in the Cricklade Museum.
An aerial shot taken from an official drone survey from 400 feet showing the ring crop mark - the mast stood in the middle - the ring was made up of smaller masts and instruments - the scars of runway #3 are on the left, runway #1 on the right and the main 2000 yard runway #2 (left to right) are clear from this angle. THERE IS NO PUBLIC ACCESS TO ANY OF THESE AREAS DUE TO PRIVATE OWNERSHIP OR TO PROTECT WILDLIFE