Double agent Eddie Chapman was one of the most colourful characters of the Second World War. Recruited by the Abwehr (German military intelligence) from a French prison, he swapped sides once he landed in Britain. Chapman, codenamed ‘Zigzag’ by the British and ‘Fritz’ by the Germans, was one of a stable of double agents in MI5’s Double Cross deception scheme, misdirecting his German handlers on a wide variety of topics. One of Zigzag’s deceptions, Operation SQUID, aimed to convince the Abwehr that Britain had a new, miracle anti-submarine weapon.
The Codebreakers at Bletchley Park helped the Allies track the progress of their deception scheme, keeping an eye out for messages relating to their operations. This series of radio messages were sent by the Abwehr, and relate to Chapman’s Operation SQUID. Intercepted and sent to Bletchley Park, they were decrypted by the section known as Intelligence Services Knox (ISK), specialists in breaking Abwehr Enigma.