Turing notebook goes under hammer
A handwritten notebook by wartime code-breaking genius Alan Turing is going on the auction block in New York today, where it is expected to bring at least one million dollars (£ 685,000).
Bonhams says the 56-page manuscript is believed to be the only extensive Turing manuscript known to exist.
The notebook was written at the time the mathematician and computer science pioneer was working to break the seemingly unbreakable Enigma codes used by the Germans throughout the Second World War.
It contains Turing's complex mathematical and computer science notations.
The story of how Turing and his team of cryptanalysts broke the code was portrayed in the film The Imitation Game, starring Benedict Cumberbatch.
The notebook dates from 1942, when they were at Britain's code and cypher school Bletchley Park. In one entry, Turing writes about a complex calculus notation.
"The Leibniz notation I find extremely difficult to understand in spite of it having been the one I understood the best once! It certainly implies that some relation between x and y has been laid down eg, y=x2+3x."
The sale also includes a working German Enigma enciphering machine. The three-rotor device, manufactured for the German military in July 1944, is estimated to sell for 140,000 to 180,000 dollars (£95,900-£123,000).
Turing was prosecuted for being gay at a time when it was illegal in Britain. 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.
Mr Gandy gave the papers to The Archive Centre at King's College in Cambridge in 1977. But he kept the notebook, using its blank pages for writing down his dreams at the request of his psychiatrist.
Bonham describes Mr Gandy's entries as highly personal; the notebook remained in his possession until he died in 1995.
At the beginning of his journal, Mr Gandy writes: "It seems a suitable disguise to write in between these notes of Alan's on notation, but possibly a little sinister; a dead father figure, some of whose thoughts I most completely inherited."
Bonhams said the seller wished to remain anonymous. Part of the proceeds will be donated to charity.