In 1926 Turing became a student at Sherborne School. The start of the first term coincided with the General Strike and as a result the railway system was not working. Turing was so determined to attend the first day that he cycled 100 km unaccompanied from Southampton to Sherborne. "By the end of his first year at the school he had gained a reputation as a shy, awkward boy whose only skills were in the area of science." (7) His housemaster complained that he started the term with a good grasp of mathematics but by the end of the year was not very good: "He spends a great deal of time in investigations in advanced mathematics to the neglect of his elementary work." (8)

John Turing, Alan's brother, later claimed that the family were well aware of his strange behaviour: "My father, on the whole, either ignored my brother’s eccentricities, or viewed them with amused tolerance but there were deep dudgeons when Alan started to accumulate appalling school reports at Sherborne... The only person in the household who was forever exasperated with Alan, constantly nagging him about his dirty habits, his slovenliness, his clothes and his offhand manners (and much else, most of it with good reason) was my mother. If this was due to some early recognition of his genius, she was certainly doing nothing to foster it by trying to press him into a conventional mould. Needless to say, she achieved nothing by it except a dogged determination on Alan’s part to remain as unconventional as possible." (9) Ben Macintyre has argued that Alan Turing was "probably on the Asperger's spectrum." (10)

At Sherborne School, Alan only had two hours a week of science lessons. The headmaster soon reported to his parents: "If he is to be solely a scientific specialist, he is wasting his time at a Public School". (11) According to Nigel Cawthorne, the headmaster told him that: "It is only the shallowest of minds that can suppose... scientific discovery brings us appreciably nearer the solution of the riddles of the universe." He considered Alan "anti-social" and said that he was "the kind of boy who is bound to be a problem in any kind of school". (12)

One of his friends, Victor Beuttell, was the son of the inventor, Alfred Beuttell. On a visit to the Beuttell family home, he began talking to Alfred about his work on his new invention, the K-ray Lighting System. As David Leavitt, the author of The Man Who Knew Too Much (2006), has pointed out: "When he asked Turing to help him fins a formula for determining what should be the proper curvature of the glass used, the boy not only came up with one immediately but pointed out that the thickness of the glass would also affect the illumination - something no one else had noticed. Beuttell gratefully made the necessary changed, and the lighting system was soon put into production." (13)

Turing came into conflict with his English and Latin teacher, A.H. Trelawney Ross who believed that Germany had lost the First World War because it thought "science and materialism were stronger than religious thought and observance." He added that "as democracy advances, manners and morals recede". Ross was furious when he caught Turing doing algebra during a study period set aside for religious instruction. He was so angry he arranged for Turing to fail both subjects. (14)

Alan Turing developed a close relationship with Christopher Morcom, a fellow student at the school. "Together they discussed the latest scientific news and conducted their own experiments. The relationship fired Turing's intellectual curiosity, but more importantly, it also had a profound emotional effect on him." (15) Turing later recalled: "During the term Chris and I began setting one another our pet problems and discussing our pet methods" and confessed that he "worshipped the ground he trod on." (16) When Alan was sixteen, "the maths master told my mother that there was nothing more that he could teach him and he would have to progress from there on his own." (17)

Alan Turing relationship with Morcom came to an end on 13th February 1930, when his friend died of tuberculosis. Turing wrote to his mother: "I feel that I shall meet Morcom again somewhere and that there will be some work for us to do together as there was for us to do here... It never seems to have occurred to me to make other friends besides Morcom, he made everyone else seem so ordinary." (18)

It has argued that Turing was devastated by the loss of the only person he would ever truly love. "His way of coming to terms with Morcom's death was to focus on his scientific studies in an attempt to fulfill his friend's potential. Morcom, who appeared to be the more gifted of the two boys, had already won a scholarship to Cambridge University. Turing believed it was his duty also to win a place at Cambridge, and then to make the discoveries his friend would otherwise have made." (19)

In 1931 Alan Turing began his studies at King's College. While at Cambridge University he became interested in politics and became a regular reader of the New Statesman. (20) He also became a follower of John Maynard Keynes and became involved in the peace-movement. (21) He joined the Anti-War Council, the purpose of which was to organize chemicals and munitions workers to strike if war was declared.

Turing enjoyed his time at Cambridge and in addition to his academic success "he found himself in a tolerant and supportive environment... homosexuality was largely accepted within the university, which meant that he was free to engage in a series of relationships without having to worry about who might find out, and what others might say." (22) He had brief sexual relationships with several men including James Atkins and Fred Clayton: "It was with Atkins that he had the extended, on-andoff sexual relationship, about which he had ambivalent feelings, because Atkins, in his mind, could not compare with the lost Christopher." (23)

In 1934 Turing attended a lecture given by Max Newman where he explained the work of German mathematician, David Hilbert. As Newman later pointed out: "The Hilbert decision-programme of the 1920's and 30's had for its objective the discovery of a general process, applicable to any mathematical theorem expressed in fully symbolitical form, for deciding the truth or falsehood of the theorem... Many were convinced that no such process was possible, but Turing set out to demonstrate the impossibility rigorously." (24)

Turing published his paper in April 1936. As Nigel Cawthorne pointed out: "What he produced was remarkable... When Newman, in his lecture, described Hilbert's 'definite method' as a 'mechanical process', he started an idea in Turing's head the future repercussions of which would be immense. The word 'mechanical' it its original sense, had referred to manual occupation, to work performed by human beings. By the 1930s, however, mechanical meant gears, rotors, vacuum tubes. It meant a machine. Turing took both definitions to heart." (25)

Alan Hodges has argued that "it is characteristic of Turing that he refreshed Hilbert's question by casting it in terms not of proofs, but of computing numbers. The reformulation staked a clearer claim to have found an idea central to mathematics." (26) To speak of a hypothetical "computing machine" at the time was to break the rules of a fairly rigid orthodoxy. "No such machines existed at the time, only calculating devices too crude to undertake any complex mathematics, and certainly not programmable." (27)

In September 1936 Alan Turing went to study under Alonzo Church at Princeton University. Over the next few months he developed the notion of a "universal computing machine" that could theoretically be programmed to solve any problem capable of solution by a specially designed machine. This concept, now called the Turing Machine, foreshadowed the digital computer. He also studied cryptology and also built three of four stages of an electro-mechanical binary multiplier. Turing studied under Albert Einstein and was offered the post as personal assistant to Professor John von Neumann, the man behind the first American computer. However, after obtaining his PhD in June 1938, he returned to Cambridge University. (28)

In June 1938, Sir Stewart Menzies, the chief of MI6, received a message that the Polish Intelligence Service had encountered a man who had worked as a mathematician and engineer at the factory in Berlin where the Germans were producing the Enigma Machine. The man, Richard Lewinski (not his real name), was a Polish Jew who had been expelled from Nazi Germany because of his religion. He offered to sell his knowledge of the machine in exchange for £10,000, a British passport and a French resident permit. Lewinski claimed that he knew enough about Enigma to build a replica, and to draw diagrams of the heart of the machine - the complicated wiring system in each of its rotors.

Menzies suspected that Lewinski was a German agent who wanted to "lure the small British cryptographic bureau down a blind alley while the Germans conducted their business free from surveillance". Menzies suggested that Alfred Dilwyn Knox, a senior figure at the Government Code and Cypher School, should go to interview Lewinski. He asked Alan Turing to go with him. They were soon convinced that he had a deep knowledge of the machine and he was taken to France to work on producing a model of the machine.

According to Anthony Cave Brown, the author of Bodyguard of Lies (1976): "Lewinski worked in an apartment on the Left Bank, and the machine he created was a joy of imitative engineering. It was about 24 inches square and 18 inches high, and was enclosed in a wooden box. It was connected to two electric typewriters, and to transform a plain-language signal into a cipher text, all the operator had to do was consult the book of keys, select the key for the time of the day, the day of the month, and the month of the quarter, plug in accordingly, and type the signal out on the left-hand typewriter. Electrical impulses entered the complex wiring of each of the rotors of the machine, the message was enciphered and then transmitted to the right-hand typewriter. When the enciphered text reached its destination, an operator set the keys of a similar apparatus according to an advisory contained in the message, typed the enciphered signal out on the left-hand machine, and the right hand machine duly delivered the plain text. Until the arrival of the machine cipher system, enciphering was done slowly and carefully by human hand. Now Enigma, as Knox and Turing discovered, could produce an almost infinite number of different cipher alphabets merely by changing the keying procedure. It was, or so it seemed, the ultimate secret writing machine." (29) Mavis Batey, who worked at the Government Code and Cypher School, pointed out the "Polish replica moved the breaking of Enigma on from a theoretical exercise to a practical one and Knox always gave the Poles credit for the part they played." (30)

On the outbreak of the Second World War the Government Code and Cypher School was established at Bletchley Park. Bletchley was selected simply as being more or less equidistant from Oxford University and Cambridge University since the Foreign Office believed that university staff made the best cryptographers. The house itself was a large Victorian Tudor-Gothic mansion, whose ample grounds sloped down to the railway station. Lodgings had to be found for the cryptographers in the town. Some of the key figures in the organization, including its leader, Alfred Dilwyn Knox, always slept in the office. (31)

Alan Turing, considered to be the country's most talented young mathematician, was one of the first people recruited to work at the Government Code and Cypher School in September 1939. A fellow codebreaker, Peter Hilton commented: "Alan Turing was unique. What you realise when you get to know a genius well is that there is all the difference between a very intelligent person and genius. With very intelligent people, you talk to them, they come out with an idea, and you say to yourself, if not to them, I could have had that idea. You never had that feeling with Turing at all. He constantly surprised you with the originality of his thinking. It was marvellous." (32)

By 1939 radio communication was a vital aspect of modern warfare. Radio was used for aerial, naval and mobile land warfare. However, it was very important that the enemy was not aware of these messages. Therefore all radio communications had to be disguised. The main task of the codebreakers was to read messages being sent by the German Enigma Machine. The situation was explained by Francis Harry Hinsley: "By 1937 it was established that... the German Army, the German Navy and probably the Air Force, together with other state organisations like the railways and the SS used, for all except their tactical communications, different versions of the same cypher system - the Enigma machine which had been put on the market in the 1920s but which the Germans had rendered more secure by progressive modifications." (33)

By studying old decrypted messages, Turing discovered that many of them conformed to a rigid structure. He found that he could sometimes predict part of the contents of an undecyphered message, based on when it was sent and its source. As Simon Singh has explained: "For example, experience showed that the Germans sent a regular enciphered weather report shortly after 6 a.m. each day. So, an encrypted message intercepted at 6.05 a.m. would be almost certain to contain wetter, the German word for 'weather'. The rigorous protocol used by any military organization meant that such messages were highly regimented in style, so Turing could even be confident about the location of wetter within the encrypted message. For example, experience might tell him that the first six letters of a particular cypher text corresponded to the plaintext letters wetter. When a piece of plaintext can be associated with a piece of cypher text, this combination is known as a crib. Turing was sure that he could exploit the cribs to crack Enigma." (34)

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The problem for Turing and the rest of the team was that at the time they had to use a "trial and error" approach. This was a very difficult task as there were 159,000,000,000,000,000,000 possible settings to check. R. V. Jones was one of those who worked with Alan Turing on this project: "Together we worked out ways in which the process might be done mechanically, with a machine that would recognize when genuine German was coming out by the frequencies with which various letters and diphthongs appeared." (35)

Another member of the team at Bletchley Park, Peter Calvocoressi, explained the task that faced the codebreakers. "Although its keyboard was simpler than a typewriter's, the Enigma machine was in all other respects much more complicated. Behind the keyboard the alphabet was repeated in another three rows and in the same order, but this time the letters were not on keys but in small round glass discs which were set in a flat rectangular plate and could light up one at a time. When the operator struck a key one of these letters lit up. But it was never the same letter. By striking P the operator might, for example, cause L to appear; and next time he struck P he would get neither P nor L but something entirely different. This operator called out the letters as they appeared in lights and a second operator sitting alongside him noted them down. This sequence was then transmitted by wireless in the usual Morse code and was picked up by whoever was supposed to be listening for it."

Both the person sending and receiving the message had a handbook that told him what he had to do each day. This included the settings of the machine. As Calvocoressi pointed out: "These parts or gadgets consisted of a set of wheels rotors and a set of plugs. Their purpose was not simply to turn P into L but to do so in so complex a manner that it was virtually impossible for an eavesdropper to find out what had gone on inside the machine in each case. It is quite easy to construct a machine that will always turn P into L, but it is then comparatively easy to find out that L always means P; a simple substitution of this kind is inadequate for specially secret traffic. The eavesdropper's basic task was to set his machine in exactly the same way as the legitimate recipient of the message had set his, since the eavesdropper would then be able to read the message with no more difficulty than the legitimate recipient. The more complex the machine and its internal workings, the more difficult and more time-consuming was it for the eavesdropper to solve this problem.... Although only three wheels could be inserted into the machine at any one time, there were by 1939 five wheels issued with each machine. The operator had to use three of this set of five. He had to select the correct three and then place them in a prescribed order. This was crucial because the wheels, although outwardly identical, were differently wired inside." (36)

In 1939 Alan Turing had a meeting with Marian Rejewski, a mathematician who had been working for the Polish Cypher Bureau. He had been trying for seven years to understand the workings of the Enigma machine. When the country was invaded by the German Army, Rejewski managed to escape to France. He told Turing that he had come to the conclusion that as the code had been generated by a machine it could be broken by a machine. In Poland he had built a machine that he named "bomba kryptologiczna" or "cryptological bomb". This machine took over 24 hours to translate a German message on an Enigma machine. Turing was impressed by what Rejewski had achieved but realised that they must find a way of achieving this in a shorter time period if this breakthrough was to be effective. (37)

Alan Turing set about developing an engine that would increase the speed of the checking process. Turing finalized the design at the beginning of 1940, and the job of construction was given to the British Tabulating Machinery factory at Letchworth. The engine (called the "Bombe") was in a copper-coloured cabinet. (38) "The result was a huge machine six-and-a-half feet tall, seven feet long and two feet wide. It weighed over a ton, with thirty-six 'scramblers' each emulating an Enigma machine and 108 drums selecting the possible key settings." (39) Its chief engineer, Harold Keen, and a team of twelve men, built it in complete secrecy. Keen later recalled: "There was no other machine like it. It was unique, built especially for this purpose. Neither was it a complex tabulating machine, which was sometimes used in crypt-analysis. What it did was to match the electrical circuits of Enigma. Its secret was in the internal wiring of (Enigma's) rotors, which 'The Bomb' sought to imitate." (40)

To be of practical use, the machine would have to work through an average of half a million rotor positions in hours rather than days, which meant that the logical process would have to be applied to at least twenty positions every second. (41) The first machine, named Victory, was installed at Bletchley Park on 18th March 1940. It was some 300,000 times faster than Rejewski's machine. (42) "Its initial performance was uncertain, and its sound was strange; it made a noise like a battery of knitting needles as it worked to produce the German keys." (43) They were described by operators as being "like great big metal bookcases". (44)

Frederick Winterbotham was the chief of Air Intelligence at MI6. He later described the moment when Major General Sir Stewart Menzies, the chief of MI6, first gave him copies of German secret messages: "It was just as the bitter cold days of that frozen winter were giving way to the first days of April sunshine that the oracle of Bletchley spoke and Menzies handled me four little slips of paper, each with a short Luftwaffe message on them... From the Intelligence point of view they were of little value, except as a small bit of administrative inventory, but to the back-room boys at Bletchley Park and to Menzies... they were like the magic in the pot of gold at the end of the rainbow. The miracle had arrived." (45)

A more improved version, called Agnus Dei (Lamb of God), was delivered on 8th August. From this point onwards, Bletchley Park was able to read, on a daily basis, every single Luftwaffe message - something in the region of one thousand a day. (46) At the time, the Battle of Britain was raging and the German codes were being broken at Bletchley Park, allowing the British to direct their fighters against incoming German bombers. When the battle was won the codebreakers intercepted messages cancelling the planned invasion of Britain - Operation Sea Lion. (47)

By 22nd May, 1940, British Military Intelligence was able, as a result of the efforts of hundreds of codebreakers decrypting the German Air Force Enigma at Bletchley, to read the most secret German Air Force commanders in France. This made it clear that the German priority was the defeat of France. Not a single Enigma message referred to any move of aircraft needed for Adolf Hitler to follow up the Dunkirk success by an assault across the Channel - Operation Sea Lion. (48)

One of the first important messages concerned the Knickebein Radio System being used by German bombers. R. V. Jones analysed this message and came to the conclusion that "it looked to me as though Knickebein might be some kind of beamed beacon which that day had been set to transmit in a north-westerly direction." Jones told Frederick Lindemann, the government's chief scientific, that he was convinced that the Germans had a radio beam transmitter called Knickebein set up at Cleves, on the nearest German soil to England and that it was part of an intersecting beam system for bombing England.

Lindemann told Winston Churchill that "there seems some reason to suppose that the Germans have some type of radio device with which they hope to find their targets". Orders were given to interrogate prisoners from the German bombers that had recently been shot down. Most refused to talk but one prisoner who professed to be anti-war admitted that the new bomb-dropping device involved two intersecting radio beams and it had been developed at Rechlin. The prisoner drew a sketch of what he thought was one of the transmitting towers which he had seen. The RAF had been collecting information about any unusual towers that had been seen in Germany. The drawing provided by the prisoner agreed exactly with a tower that had been photographed near an airfield at Hörnum.

Jones was called to a meeting of the War Cabinet: "Churchill asked me what we could do. I told him that the first thing was to confirm their existence by discovering and flying along the beams for ourselves, and that we could develop a variety of counter-measures ranging from putting in a false cross-beam to making the Germans drop their bombs early, or using forms of jamming ranging from crude to subtle... And then the meeting ended. There were no minutes, because the matter seems to have been deemed so secret that no secretaries were present, and the only record was the one that I made for my report written during the following week."

Following further investigations it was discovered that Jones's predictions had been correct: "Our conclusions had been confirmed: there were indeed two beams, whose bearings were consistent with transmitters at Cleves and Bredstedt.... All doubts were now removed, and plans for counter-measures could go urgently ahead." In his final report to Churchill, R. V. Jones argued: "There are many lessons in this story, most of which are too obvious to point out. It shows the German technique is well-developed - almost beyond what we thought possible." (49)

Greg Goebel, the author of The Battle of the Beams (2013) has pointed out that by September, 1940, the British had found a way of dealing with Knickebein: "The British were operating more powerful anti-Knickebein transmitters that degraded Knickebein signals by injecting them with Morse code patterns. Since the beams were codenamed 'Headaches', the transmitters were named 'Aspirins'. Knickebein had been neutralized. Without direction, German bombers sometimes got lost in the dark, and at least one crashed because the pilot became completely disoriented, losing control of his aircraft and causing his crew to bail out before the bomber slammed into the ground." (50)

In June 1940 Joan Clarke went to work for Alan Turing in Hut 8. Joan later recalled: "I can remember Alan Turing coming in as usual for a day's leave, doing his own mathematical research at night, in the warmth and light of the office, without interrupting the routine of daytime sleep." (51) The two quickly developed a close relationship. He found her intellectually satisfying as she was able to discuss papers he had written. They were also both keen on chess and although Joan had only recently learnt to play, they were quite well matched. "As they only had a cardboard pocket set, and proper pieces were unobtainable in wartime conditions, so they improvised their own solution. Alan got some clay from one of the local pits, and they modelled the figures together. Alan then fired them on the hob of the coal fire in his room at the Crown Inn. The resulting set was quite usuable, if somewhat liable to breaking. He also tried to make a one-valve wireless set, telling her about the one he had made at school, but this was not such a success." (52)

Alan Turing eventually proposed marriage and Joan Clarke gladly accepted. (53) Nigel Cawthorne, the author of The Enigma Man (2014) suggests that "Turing was not much of a catch... Sometimes he appeared in the office in his pyjamas, or wore trousers held up by a striped necktie instead of a belt. His hair was unkempt and he had a permanent five o'clock shadow, refusing to shave with anything but an ancient electric razor. Though he did not smoke, his teeth were yellow and he bit his fingernails. He was also a workaholic." (54)

A few days later he told her that the marriage might have problems as he had "homosexual tendencies." (55) Clarke's biographer, Lynsey Ann Lord, has argued: "To understand her decision to continue with the engagement following his disclosure, it has to be made clear that during this period in history, marriage for many women, was considered a social duty and it was not necessary that marriage should correspond with sexual desires." Alan Hodges agrees and claims that "many people, in 1941, would not have thought it important that marriage did not correspond with his sexual desires; the idea that marriage should include a mutual sexual satisfaction was still a modern one, which had not yet replaced the older idea of marriage as a social duty. One thing that Alan never questioned was the form of the marriage relationship, with the wife as housekeeper." (56)

The engagement was continued and he gave her a ring. Alan also took Joan to Guildford to meet his mother. They also had lunch with her parents, William and Dorothy Clarke. Alan told Joan about some of his homosexual relationships but claimed that this kind of behaviour was over. He even said that he would like them to have children. However, he eventually decided that he could not go through with the marriage and broke the relationship off. (57)

On 6th September, 1941, Prime Minister Winston Churchill and Sir Stewart Menzies, the head of MI6, visited Bletchley Park. Churchill was shocked by the wide variety of backgrounds of the codebreakers: "In addition to the mathematicians and linguists, there was an authority on porcelain, a curator from the Prague Museum, the British chess champion and numerous bridge experts." Churchill told Menzies: "I told you to leave no stone unturned, but I didn't expect you to take me so literally." (58)

Turing believed that Bletchley Park needed more staff to carry out the task of dealing with so many secret German messages. On 21st October 1941, Turing wrote to Churchill: "Some weeks ago you paid us the honour of a visit, and we believe that you regard our work as important. You will have seen that, thanks largely to the energy and foresight of Commander Travis, we have been well supplied with the 'bombes' for the breaking of the German Enigma codes. We think, however, that you ought to know that this work is being held up, and in some cases is not being done at all, principally because we cannot get sufficient staff to deal with it. Our reason for writing to you direct is that for months we have done everything that we possibly can through the normal channels, and that we despair of any early improvement without your intervention." (59)

Churchill told his principal staff officer: "Make sure they have all they want on extreme priority and report to me that this has been done." By the end of 1942 there were 49 Turing machines. As part of the recruitment drive, the Government Code and Cypher School placed a letter in the Daily Telegraph. They issued an anonymous challenge to its readers, asking if anybody could solve the newspaper's crossword in under 12 minutes. It was felt that crossword experts might also be good codebreakers. The 25 readers who replied were invited to the newspaper office to sit a crossword test. The six people who finished the crossword first were interviewed by military intelligence and recruited as codebreakers at Bletchley Park. (60)

After the death of his boss, Alfred Dilwyn Knox, in February, 1943, Turing became the chief consultant to the vast cryptanalytic operation. By this time Ultra had become a major industry and employed some 6,000 people to translate over 2,000 messages a day. However, Turing was suffering from stress: "Turing was a man of enormous intellect but, by then, few reserves of nervous energy. He was nearing the end of his tether as he coaxed his battery of engines at Bletchley to penetrate Enigma-enciphered U-boat communications and pinpoint the movements of his fearful enemy." (61)

Alan Turing behaviour became more eccentric. "He would convert the family money into silver ingots at the outbreak of war, bury them, and then forget where they were. He corresponded with friends in a cipher punched onto a tape which no one could read. He was a talented long-distance runner and would on occasion arrive at conferences at the Foreign Office in London having run the 40 miles from Bletchley in old flannels and a vest with an alarm clock tied with binder twine around his waist." (62) His friend, Geoffrey Jefferson, described his "long, disturbing silences punctuated by a cackle" that "wracked the nerves of his closest friends." He added that he was "so unversed in worldly ways, so child-like, so non-conformist, so very absent-minded... a sort of scientific Shelley." (63)

However, his brother, John Turing, believes some of these stories were exaggerated. He was especially critical of Ronald Lewin, the author of Ultra Goes To War (1978) who said that "in some fit of despondency Alan converted all his money into cash and buried it in the Bletchley woods as a reserve against disaster." John Turing claims that: "In fact, he did nothing of the kind. He had decided that if there were a German invasion, banking accounts would be useless, so he bought some silver ingots for use on the black market. These he trundled in an ancient perambulator and buried in a field (not at Bletchley), where he made a sketch map of their position so he could find them after the war. After the war, he enlisted the help of his friend, Donald Michie (now Professor Michie of Edinburgh University), to dig up these ingots - using, typically, a homemade metal detector - but the heavy ingots were by now well on their way to Australia and were never seen again." (64)

According to his biographer, Alan Hodges, Turing became very interested in electronics during the later stages of the war: "Electronics... made its first appearance at Bletchley as telephone engineers were pressed into an effort to enable the machines to work at ever higher speeds, and thus Turing was introduced to the potential of this new and untried technology. He himself devoted much time to learning electronics, ostensibly for his own, elegant, speech secrecy system, effected with one assistant, Donald Bayley, at nearby Hanslope Park. However, he had a more ambitious end in view: in the last stage of the war (for his part in which he was appointed OBE), he planned the embodiment of the universal Turing machine in electronic form, or, in effect, invented the digital computer.... In 1944 Turing knew his own concept of the universal machine; the speed and reliability of electronics; and the inefficiency of building new machines for new logical processes. These provided the principle, the means, and the motivation for the modern computer, a single machine capable of any programmed task. He was spurred by a fourth idea that the universal machine should be able to acquire the faculties of the brain."

It has been claimed that Turing's work enabled much of modern technology to take place: "Turing was captivated by the potential of the computer he had conceived. His earlier work had shown the absolute limitations on what any Turing machine could do, but his fascination now lay in seeing how much such machines could do, rather than in what they could not, and in the power of the concept of the universal machine. Indeed from now on he argued that uncomputable functions were irrelevant to the problem of understanding the action of the mind. His thought became strongly determinist and atheistic in character, holding that the computer would offer unlimited scope for practical progress towards embodying intelligence in an artificial form." (65)

After the war Alan Turing lived in Richmond while he worked on the design of the ACE (Automatic Computing Engine) at the National Physical Laboratory (NPL). In 1947 he returned to Cambridge University and produced an unpublished paper on Intelligent Machinery. In 1948, he was appointed Reader in the Mathematics Department at the University of Manchester. The following year he became Deputy Director of the university's Computing Laboratory and produced software for one of the earliest stored-program computers. (66)

In 1950 he addressed the problem of artificial intelligence. He developed what became known as the Turing Test. He stated that with a person in one room and the machine in another, an interrogator in a third room asks questions of both to try to identify them. When the interrogator cannot distinguish between them by questioning, the machine will have reached a state of human-like intelligence.

In December 1951 Alan Turing met Arnold Murray, a 19-year-old unemployed man while walking the streets of Manchester. "Alan invited him to lunch in the restaurant across the road. Fair and with blue eyes, undernourished and with his thin hair already receding, desperate for better things and more receptive than so many educated people, Arnold touched Alan's soft spot for lost lambs, as well as other cords." Turing told him about his work and Arnold pleased him by asking sensible questions about his research. (67)

They agreed to meet again and on 12th January 1952, Arnold visited Alan's home in Wilmslow. Two days later he spent the night with Alan. Not wanting to be treated as a prostitute, "Arnold rebuffed Turing's efforts to give him cash." The following day he noticed that £10 was missing from his wallet. When he saw him later that week he accused Arnold of stealing his money. He denied it but admitted he was in debt and asked for a loan of £3. On 18th January Arnold asked him for another £7. (68)

On 23rd January he arrived home to find his house burgled. He wrote to his friend, Fred Clayton: "I have just had my house broken into, and am still every few hours finding some fresh thing missing. Fortunately I am insured, and little has gone that is really irreplaceable. But the whole thing has had a very disturbing effect, especially as it followed shortly on a theft from me at the University." (69)

Alan Turing reported the burglary to the police and two CID officers came to take fingerprints in the house. On 2nd February, Arnold returned to Alan's house. After having a few drinks together Arnold admitted that a friend of his, Harry, a twenty-year old unemployed man, was responsible for the burglary. The following morning Alan reported this information to the police. Harry was in custody on another charge and they had already matched his fingerprints with those found in Alan's house. The CID officers began to ask him about his relationship with Arnold. He confessed to having a homosexual relationship with Arnold and then wrote a five page statement giving full details of what had taken place between the two men. Alan added that he was convinced that Parliament was just about "to legalize it". Arnold was now arrested and both men were charged with gross indecency under Section 11 of the Criminal Law Amendment Act 1885. (70)

Turing wrote to Joan Clarke, who was now engaged to be married to Lieutenant-Colonel J. K R Murray. (71) He admitted that he had been having sex with other men and that "he had been found out". He tried to assure her that he would not be sent to prison and claimed that "they're not as savage as they used to be". He had been told that only 174 of the 746 men prosecuted for gross indecency had been imprisoned, and then mostly for less than six months. He was also a "first offender" which diminished the chances of imprisonment. (72)

Turing and Murray went on trial on 31st March 1952. Max Newman and Hugh Alexander both appeared as character witnesses. Turing and Murray were found guilty. Murray was given a conditional discharge. Turing was placed on probation, which would be conditional on his agreement to undergo hormonal treatment designed to reduce his sex drive. He accepted the option of treatment via injections of stilboestrol, a synthetic oestrogen; this treatment was continued for the course of one year. Turing wrote to his friend, Philip Hall: "I am both bound over for a year and obliged to take this organo-therapy for the same period. It is supposed to reduce sexual urge whilst it goes on... The psychiatrists seemed to think it useless to try and do any psychotherapy." (73) The treatment rendered Turing impotent.

Turing's conviction led to the removal of his security clearance and barred him from continuing with his cryptographic consultancy for the Government Communications Headquarters (GCHQ). The case of the two Soviet spies, Guy Burgess and Donald Maclean, who were both homosexuals, convinced the authorities that Turing was a security risk and was forbidden to work on research projects relating to the development of the computer. (74) He was also denied entry into the United States.

At his home in Wilmslow he began making certain chemicals, among them potassium cyanide. On 7th June, 1954, he coated an apple with some of the cyanide, went to bed and bit the apple and died. The coroner pronounced at the inquest: "I am forced to the conclusion that this was a deliberate action, for with a man of this type one can never be sure what his mental processes are going to do next. Here was a brilliant mathematician with unusual mental achievements. he might easily become unbalanced and unstable." (75)

Alan Turing - School Student (Answer Commentary)

(1) Alan Hodges, Oxford Dictionary of National Biography (2004-2014)

(2) Sara Turing, Alan M. Turing (1959) page 11

(3) David Leavitt, The Man Who Knew Too Much (2006) page 9

(4) Nigel Cawthorne, The Enigma Man (2014) page 18

(5) Sara Turing, Alan M. Turing (1959) page 15

(6) David Leavitt, The Man Who Knew Too Much (2006) page 21

(7) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 166

(8) Sara Turing, Alan M. Turing (1959) page 27

(9) John Turing, He Should be Alive Today (22nd June, 2012)

(10) Ben Macintyre, The Real Alan Turing (15th November, 2014)

(11) Alan Hodges, Alan Turing: the Enigma (1983) page 26

(12) Nigel Cawthorne, The Enigma Man (2014) pages 21-22

(13) David Leavitt, The Man Who Knew Too Much (2006) page 15

(14) Nigel Cawthorne, The Enigma Man (2014) page 23

(15) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 166

(16) Alan Hodges, Oxford Dictionary of National Biography (2004-2014)

(17) John Turing, He Should be Alive Today (22nd June, 2012)

(18) Alan Turing, letter to Sara Turing (16th February, 1930)

(19) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 166

(20) Nigel Cawthorne, The Enigma Man (2014) page 20

(21) Alan Hodges, Oxford Dictionary of National Biography (2004-2014)

(22) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 169

(23) Nigel Cawthorne, The Enigma Man (2014) page 20

(24) Max Newman, The Hilbert Decision Programme, included in Mathematical Logic (2001) page 272

(25) Nigel Cawthorne, The Enigma Man (2014) page 54

(26) Alan Hodges, Alan Turing: the Enigma (1983) page 8

(27) Nigel Cawthorne, The Enigma Man (2014) page 58

(28) Mavis Batey, Oxford Dictionary of National Biography (2004-2014)

(29) Anthony Cave Brown, Bodyguard of Lies (1976) page 21

(30) Mavis Batey, Oxford Dictionary of National Biography (2004-2014)

(31) Penelope Fitzgerald, The Knox Brothers (2002) page 228-229

(32) Sinclair McKay, The Secret Life of Bletchley Park (2010) pages 16 and 17

(33) Francis Harry Hinsley, British Intelligence in the Second World War: Volume One (1979-1990) page 53

(34) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 170

(35) R. V. Jones, Most Secret War: British Scientific Intelligence 1939-1945 (1978) page 100

(36) Peter Calvocoressi, Top Secret Ultra (1980) pages 34-37

(37) Nigel Cawthorne, The Enigma Man (2014) page 55

(38) Sinclair McKay, The Secret Life of Bletchley Park (2010) page 95

(39) Nigel Cawthorne, The Enigma Man (2014) page 55

(40) Harold Keen, interviewed by Anthony Cave Brown (c. 1970)

(41) Anthony Cave Brown, Bodyguard of Lies (1976) page 23

(42) Nigel Cawthorne, The Enigma Man (2014) page 58

(43) Alan Hodges, Alan Turing: the Enigma (1983) page 231

(44) Mary Stewart, interviewed in the documentary The Men Who Cracked Enigma (2003)

(45) Frederick Winterbotham, The ULTRA Secret (1974) page 15

(46) Sinclair McKay, The Secret Life of Bletchley Park (2010) page 98

(47) Nigel Cawthorne, The Enigma Man (2014) page 58

(48) Martin Gilbert , The Second World War (1989) page 82

(49) R. V. Jones, Most Secret War: British Scientific Intelligence 1939-1945 (1978) pages 150

(50) Greg Goebel, The Battle of the Beams (1st February, 2013)

(51) Nigel Cawthorne, The Enigma Man (2014) pages 65

(52) Alan Hodges, Alan Turing: the Enigma (1983) pages 260-261

(53) Lynsey Ann Lord, Joan Clarke Murray (2008)

(54) Nigel Cawthorne, The Enigma Man (2014) pages 64-65

(55) Lynsey Ann Lord, Joan Clarke Murray (2008)

(56) Alan Hodges, Alan Turing: the Enigma (1983) page 259

(57) David Leavitt, The Man Who Knew Too Much (2006) page 178

(58) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 178

(59) Alan Turing, letter to Winston Churchill (21st October, 1941)

(60) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 181

(61) Anthony Cave Brown, Bodyguard of Lies (1976) page 253

(62) Sara Turing, Alan M. Turing (1959) page 58

(63) Ben Macintyre, The Real Alan Turing (15th November, 2014)

(64) John Turing, He Should be Alive Today (22nd June, 2012)

(65) Alan Hodges, Oxford Dictionary of National Biography (2004-2014)

(66) Simon Singh, The Code Book: The Secret History of Codes & Code-Breaking (2000) page 189

(67) Alan Hodges, Alan Turing: the Enigma (1983) page 566

(68) David Leavitt, The Man Who Knew Too Much (2006) page 266

(69) Alan Turing, letter to Fred Clayton (24th January, 1952)

(70) Alan Hodges, Alan Turing: the Enigma (1983) page 576

(71) Lynsey Ann Lord, Joan Clarke Murray (2008)

(72) Alan Hodges, Alan Turing: the Enigma (1983) page 588

(73) Alan Turing, letter to Philip Hall (17th April 1952)

(74) Anthony Cave Brown, Bodyguard of Lies (1976) pages 814

(75) Wilmslow County Express (10th June, 1954)