Margaret Thatcher benefited during the Falklands conflict from a spy programme that duped more than 120 countries, including Argentina, into buying communications hardware that allowed their messages to be intercepted by the CIA.

For more than 50 years a Swiss company, Crypto AG, was trusted by clients including the Vatican, Iran, India, Pakistan, several Nato powers and Latin American juntas to provide encryption devices that secured the communications of their spies, diplomats and military. None of its customers knew that behind Crypto AG lay a classified partnership between its joint owners: the CIA and the West German (and later German) intelligence agency BND.

The operation has only been exposed now in a project by The Washington Post and ZDF, a German public broadcaster. It reviewed