Today Alan Turing is a household name - famed as the code-breaking genius who helped Britain defeat the Nazis in the Second World War.
But the Turing sold to us in fiction - most recently in Hollywood's retelling of how Turing helped British intelligence crack the German military's Enigma code - differs from the man that family and friends recall.
Alan Turing's nephew, Sir Dermot Turing, has gathered accounts from those close to the brilliant mathematician for a new biography. Those testimonies reveal what he was truly like and uncover more about what he did in the later part of the war. They also bring to light new facts that undermine conspiracy theories about an official cover-up of the events leading to Turing's untimely death in 1954.
The real Turing
When portrayed in film and newspaper reports, Turing is sometimes caricatured as a prickly figure who made others uncomfortable.
But those who remember Turing from his days at the British codebreaking nerve centre at Bletchley Park describe a different figure, one who could be tricky to keep up with, but who was also bright and sparky.
"The image that I had when I started this work was of somebody who was rather eccentric, unapproachable, possibly a bit solitary and rather difficult to deal with," said Sir Dermot.
"If that is the common picture then I have to say that is a bit a mythical. I found someone who was much more human."
Turing may have satisfied the cliche of being socially-awkward and diffident when outside of his comfort zone - but that was not all he was.
"It's absolutely right that if you put him in a sherry party environment then he would have hated it and probably would have been the most appalling and unsuitable guest.
"But on the other hand if you put him with his friends who shared a common interest in the more technical things then he was vibrant, humorous, fun to be with and social."
In first hand accounts and recollections of Turing, Sir Dermot uncovered stories of a man who, in the little downtime during the round-the-clock operation to decrypt Nazi messages, was "happy playing chess in the pub and talking to his Bletchley Park mates about how you might devise a chess playing program for a computer that nobody had built yet."
Rather than being someone who was "impossible to deal with", Sir Dermot found a more common complaint was that "he was difficult to follow if he was explaining something". Perhaps an understandable complaint about a man sometimes credited with being the father of artificial intelligence and theoretical computer science.
Conspiracy theories and cover-ups
Turing died at the age of just 41, with the official cause of death being cyanide poisoning.
In the years running up to his death, Turing suffered a great deal at the hands of the state he had helped so much. In 1952 he was convicted of gross indecency for having an affair with a man, at a time when all homosexual activity was illegal. Rather than go to prison, Turing accepted probation on the condition he underwent chemical castration. The treatment had various unpleasant side-effects and Turing - whose conviction resulted in his clearance to work for the British intelligence agency GCHQ being revoked - continued to be harassed by police surveillance.
Even though an inquest returned a verdict of suicide, there has been speculation as to whether Turing's death was accidental - the result of inadvertently inhaling cyanide fumes from experiments he'd conducted at home. The lack of a suicide note and some signs that he was in a cheerful mood and planning chores for the week ahead have been cited as evidence for this theory.
But among his father's correspondence file Sir Dermot found indications of fresh turmoil in Turing's life in the period leading up to his death.
"Another thing that was very interesting in that file was that it suggested that Alan Turing was having trouble with another of his boyfriends at the time," he said.
"There was reference to a man called Roy, and I've been unable to track down Roy or find out anymore information than is in this file, but it looks as if there was at least a possibility a new scandal was about to break.
"If that's the correct way to read these documents then that does cast a new light onto what Alan's state of mind might have been that weekend."
Some have even gone as far as to suggest Turing may have been murdered by the FBI to cover up revelations that Russian double agents had risen to prominent positions in the US government. They claim Turing learned this information when deciphering Soviet messages during the war.
But Sir Dermot believes the speed with which Turing's inquest was arranged - within days of his death on the Monday - makes it unlikely that his death was subject to such an elaborate cover-up.
"My father found out about his brother's death while he was at a cinema on a Tuesday evening and the telephone note that was left for him when he came back from the cinema said that the inquest was going to be held on the Thursday," he said.
"The inquest date had been set with remarkable rapidity. There wasn't any time for anybody to influence or manipulate any evidence."
Alan Turing - the lost years
Apart from his seminal work on devising a 'Universal Machine', a paper that laid the foundation for computer science, Turing is most famous for his role in decrypting the Enigma code the German military used to scramble its messages.
Turing's breakthrough was in designing the British Bombe, a machine that emulated the workings of 36 Enigmas. The Bombes were able to rapidly check each of the many ways that Enigma could encipher messages. Automating the process was a must, as even after the number had been narrowed down, there were still just over one million possibilities.
But Turing's work on code-breaking had "pretty much run its course by the middle of 1942", according to Sir Dermot. So what was Turing doing for the remainder of the war? New documents that GCHQ is in the process of releasing to the public and which Sir Dermot had access to when writing the book shed light on what he calls the "missing years".
"He was essentially moved from being a codebreaker to somebody who was responsible for the Allied communications security."
During this time Turing worked on voice encryption, so that UK prime minister Winston Churchill could have a telephone conversation with US president Franklin D. Roosevelt without fear of eavesdropping - something that Sir Dermot said had previously been happening. Turing also spent a while working on how to encipher messages sent via telegraph and radio.
"Previous accounts of what he'd been doing during that period had been incomplete. We've now got a much better picture."
Even though Sir Dermot never got to meet his uncle, he said that researching the book has allowed him build up an image that he feels is closer to Turing the person, rather than the myth.
"It's the character that we see and it's not a true picture in some sense. It's been nice to be able to build up a slightly different picture."
- Sir Dermot's biography of Alan Turing Prof: Alan Turing Decoded is published by The History Press and available now.
Nick Heath is chief reporter for TechRepublic. He writes about the technology that IT decision makers need to know about, and the latest happenings in the European tech scene.