Menwith Hill, North Yorkshire

Menwith Hill Base near Harrogate, North Yorkshire, is the largest electronic monitoring station in the world. Run by the US National Security Agency (NSA), it is one of a global network of Signals Intelligence (SIGNIT) bases, codenamed ECHELON. The Menwith Hill site covers 560 acres of land and includes 4.6 acres of buildings.

The 23 golf-ball like radomes house satellite dishes, which, along with high frequency radio supports and fibre optic cables, intercept communications from Europe, Russia, the Middle East and North Africa. All telecommunications traffic to and from Europe and passing through Britain can be intercepted at the base, including private telephone calls, faxes, and emails.

Spies Among Us