A rare and exceptionally well-preserved example of the World War II cipher machine, The Enigma, is due to be auctioned later. The machine had a huge impact on the course of 20th-century history, playing a critical role in the codebreaking story that unfolded at Bletchley Park.
Used by Nazi forces during World War II to transmit coded messages - and with around 159 million million million possible settings - the German command was convinced that the Enigma machine produced an unbreakable code.
Famously, Alan Turing and the team at Bletchley Park proved otherwise and their ground-breaking work is said to have shortened the war by two years and saved up to 22 million lives.
Many Enigma machines were destroyed by the Germans as they retreated at the end of the war and the example going under the hammer today could fetch between £50,000 and £70,000.
Christie's is selling a German three-rotor Enigma cipher machine, from around 1939, as part of its natural history sale next month. The code machine, estimated to be worth £40,000-£60,000 was widely used during World War II to encrypt and decode messages sent between the military and its commanders.
Its interchangeable rotors made a total of 15 billion billion possible readings for each character. This was considered too complex to be broken, but due to the efforts of Alan Turing and a team of analysts at Bletchley Park, the mechanism was cracked, enabling the allies to read all secure messages