This site was associated from 1968-1973 with the top secret Anglo-American System 441A 'over the horizon' backscatter radar project code-named 'Cobra Mist'. This project was set up to carry out several 'missions' fulfilling intelligence requirements and providing a research and development test-bed. These were signified by 18 'strings' of antennae, which stood in the shape of a large open fan and a large aluminium 'ground net' covering about 80 acres of the exterior Lantern Marsh landscape north of the site.

In addition Cobra Mist was well known for its alleged associations with UFOs and the large grey steel building also housed BBC World Service radio transmitters operated by Merlin International Ltd, until late 2011 (Source: National Trust Website for Orford Ness)