Presented by Rene Cutforth
Saturday evening, 7 January 1961. Superintendent Smith of Scotland Yard arrests the Krogers at their Ruislip bungalow. The Portland Spy Ring is broken.
The Krogers were probably the most capable spies ever caught - their coding and communications techniques, models of efficiency and security. But how did their sophisticated devices work? The innocent-looking talc tin and whisky flask? The transmitter with the high-speed keying device? The one-time code pads? The microdots?