Wartime code-cracking genius Alan Turing's handwritten notebook went under the hammer at Bonham's in New York today, where it sold for just over £700,000.
Written in 1942, while the mathematician was wrestling to beat the Germans' famously 'unbreakable' Enigma code, the 56-page book is believed to be the only significant handwritten Turing manuscript in existence.
The book contains the so-called father of computer science's complex mathematical notations from his time at Bletchley Park, the Allies' code-breaking headquarters during World War 2.
ITV News reporter Richard Pallot explains:
The auction also features a working German Enigma enciphering machine. The three-rotor device, manufactured for the German military in July 1944, sold for £163,000.
Despite being an unsung hero of the war effort, Turing was subsequently prosecuted for being gay, which was illegal in Britain at the time. He was convicted of indecency in 1952 and agreed to undergo hormone treatment as an alternative to imprisonment to 'cure' his homosexuality.
He died in 1954 of cyanide poisoning, which was ruled a suicide, although his family and friends believed it might have been accidental. The notebook was among the papers he left in his will to friend and fellow mathematician Robin Gandy.