A postcard Alan Turing sent his psychologist while on holiday in Corfu has sold for $35,000 at RR Auction.
It last sold for £13,750 ($17,172) at Bonhams in 2015, resulting in phenomenal growth of 42.7% per annum.
Turing became close friends with his psychologist, Dr Franz Greenbaum
The postcard dates to 1953 and reads: "I hope you are all enjoying your selves as well as I am here at Corfu.
“It is tremendously hot and one wears bathing things all day."
Turing is most famous as the genius behind the cracking of the German Enigma code during the second world war.
He was also the father of modern computer science.
Unsurprisingly, given his fascination with codes and ciphers, the postcard has a hidden message.
The image it displays is from first century scholar and military leader Flavius Josephus’ book Antiquities of the Jews.
It was probably chosen in reference to the Josephus Problem.
In the book Josephus explains that he managed to survive a mass suicide pact organised by his men to avoid capture from Roman forces. Each was to stab the man to his left.
Mathematicians have been working out the solution as to where Josephus stood in the circle ever since.
The Robert Livingston, of the US-based RR Auction, said: “Turing, who was fascinated by these types of algorithmic puzzles, surely knew of the ‘Josephus Problem’ and it is likely the reason he chose this specific postcard.
“Connecting mathematics through the ages, this is a truly remarkable piece.”
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