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Alan Turing
Decoding a Life

By Tomas Elliott

Perhaps the reason why the life and legacy of Alan Turing (1912–1954) continue to fascinate is because they intersect with some of the great highs and lows of twentieth-century British history. From the heroic climax of his decryption of the Enigma cipher at Bletchley Park, to the tragedy of his prosecution for homosexuality and his subsequent suicide, Turing experienced the best and worst of the powerful machinations of the modern British state. Since his death, the reception of his legacy has highlighted a public effort to grapple with the prejudices of the past.

Nowadays, Turing’s life and his major achievements are widely known. Having grown up in London and South England, he attended Sherborne School, an independent boarding school in Dorset. There is a famous anecdote about Turing’s first day, which coincided with the 1926 General Strike. Determined not to miss class, Turing cycled 63 miles unaccompanied—he was 13 years old at the time—all the way from Southampton to Sherborne. While he would later be remembered for his uncompromising intellect, he also never lost his athleticism. When he was at Bletchley, he would sometimes run the 40 miles back to London just to attend a meeting in the city, and in 1948 he tried out for the British Olympic running team.

Alan Turing, aged 16

At Sherborne, however, Turing did not always dazzle. In his correspondence with Turing’s school friends, Turing’s later biographer, Andrew Hodges, noted that he had a “rather chequered career at Sherborne School.” His teachers sometimes complained that his inclination for maths and science led him to neglect his other subjects, and his headmaster once wrote to his parents to tell them that Turing “must be educated. If he is to be solely a Scientific Specialist, he is wasting his time at a public school.”

That penchant for specialization, however, would later serve Turing well at King’s College Cambridge, where he graduated with first class honours in mathematics in 1934. The following year, he was elected as a Fellow of the college, aged just 22. The year after that, while still a PhD student, he published what has since become known as “the most influential maths paper in history,” entitled “On Computable Numbers, with an Application to the Entscheidungsproblem” (1936).

In that paper, Turing formed the theoretical basis for a “universal computing machine,” which he proved would be capable of solving any computational problem, provided that the problem could be represented as an algorithm. All that was required was a machine with sufficient power to process and record the information. Although, at the time, Turing’s ideas were not widely understood beyond a few specialists, they set him up for his work in cryptography during World War II, which famously led to the decoding of Nazi Germany’s Enigma machine. Despite being one of the most significant breakthroughs of the war, however, Turing’s work remained classified for years. Some of his discoveries were not made public until as late as April 2012, since GCHQ continued to rely on them as part of their training modules, demonstrating just how important and far-reaching they were.

The Colossus machine at Bletchley Park. By Unknown author – This file is from the collections of The National Archives (United Kingdom), catalogued under document record FO850/234.

A memoir about Turing was written, however, not long after his death in 1954. It was penned by his mother, Sara Turing, who sought to highlight her son’s achievements without mentioning his classified war work. As well as describing his theoretical discoveries at Cambridge, the memoir drew attention to Turing’s work after the war, in which his “logical theory of a universal machine” took “concrete form in an actual machine”: the early computer. During this time, Turing also provided a foundational theory of artificial intelligence in his 1950 paper, “Computing Machinery and Intelligence,” in which he outlined his celebrated “imitation game,” later known as the Turing test.

Although she provided a sensitive record of her son’s work, Sara Turing either did not realize or did not want to admit that her son’s death, which had occurred when he was just 41, had been suicide. She also neglected to mention his homosexuality, even though she knew that he was living as an openly gay man (illegally at the time). It would be left to Andrew Hodges in his later and more comprehensive biography, Alan Turing: The Enigma, published in 1983, to explore those matters in detail, while also revealing much more about Turing’s time at Bletchley. In this work, Hodges documented how Turing was convicted for “gross indecency” in 1952 and, to avoid a prison sentence, was forced to undergo a form of drug-induced castration, intended to reduce his libido. Following his conviction, Turing wrote a letter to his friend Norman Routledge, which he closed with a poignant, three-line reflection on the reception of his work:

Turing believes machines think
Turing lies with men
Therefore machines do not think
Yours in distress, Alan.

TURING, Sara. Alan M. Turing. 1959.
HODGES, Andrew. Alan Turing: The Enigma. 1983.

If the faulty logic of this syllogism intentionally encapsulates the fickleness of the state’s betrayal of one of its former heroes, it also highlights the senseless, mechanistic operations of the state itself—yet another man-made machine not capable of thinking. The in-built prejudices of that machine would take more than 60 years to reprogram. Turing would not receive a pardon for the crime of “gross indecency” until 2013. It would take until 2016 for that pardon to be extended to others previously convicted of the crime.

This shows just how revolutionary Hodges’ 1983 biography was in and of itself. Alan Turing: The Enigma raised its subject from obscurity at a time when his life had been all but forgotten, even hushed up. Reflecting on that biography in 2014, after Turing’s pardon, Hodges remarked that the reception of Turing’s legacy had been as dependent on gay liberation as it had been on Britain’s victory over Nazi Germany: “the 1968 social revolution, which Turing anticipated, had to happen before his story could be liberated.” If Turing produced seismic shifts in understanding in his life, in other words, then his legacy awaited similar shifts before it could be recognized. The biographic and bibliographic histories of Turing, therefore, speak to the changing landscapes within which history is made and remade, pointing to the need to examine the stories we tell and decode the ones that we don’t.


Andrew Hodges’ biography of Turing appears in our catalogue Spring 2021.