Alan Turing: The Enigma The Centenary Edition

by Andrew Hodges

  The British government was well-disposed to finding scientific solutions to its problems, and had announced on 5 February a grand plan to plant its East African colonies with groundnuts. The ACE, likewise, though it represented only a fraction of the investment in the groundout scheme, was still in 1947 a highly progressive project. It was just what the left-wing pressure groups had called for in the 1930s, with the state taking over the development of new science and technology instead of leaving it to the caprice of commerce. Blackett, as president of the Association of Scientific Workers, was at the vanguard of this movement. In 1947 he wrote an introduction to the ASW book Science and the Nation, which promised such modern wonders as ‘the scientific organisation of bureaucracy’. Yet the application in peacetime of such scientific policies was liable to go in unforeseen directions. Blackett himself, by enticing F.C. Williams to work on a pure-mathematical computer at Manchester, had not exactly helped the national plan. And although a left-wing advocate of planning, he had shown considerable personal dash and enterprise. Darwin’s position was more paradoxical still. Whether for hereditary or other reasons, he held the right-wing views of a Social Darwinist, taking a dim view of the welfare state.42(’The policy of paying most attention to the inferior types is the most inefficient way possible of achieving the perfectibility of the human race.’) His recipe for progress, or rather for a check to what he considered to be European racial suicide, was that men who had been ‘promoted’ should endeavour to have more children than others. Yet the dispensations of the NPL resembled less the jungle of cut-and-thrust competition than the ham-fisted management of the Soviet Union. They did not create an environment in which variety and initiative could long survive.

  In the spring of 1947, while Darwin applied the higher realms of his thought to solving the problem of Alan Turing, incoherent initiatives were taken by more impatient people on the lower rungs of the promotion scale. One of these was Harry Huskey, who was very eager to see a start made on building a computer before his year was out. He admired the general form of the ACE design, but believed that the best plan would be to construct a small delay line machine ‘on a plan which is a compromise between the NPL and the Moore School plans.’ Relations between Alan and Huskey had been cool from the start, but they deteriorated when one day in the spring, Alan went into Mike Woodger’s room to find him engaged upon writing a program headed ‘Version H’. This was in fact an adaptation by Huskey of the Version V of the ACE, trimmed to include only the barest minimum of apparatus required to do a useful job, which was defined as the solution of eight simultaneous equations.* Though generally consistent with the ACE design philosophy, such a departure necessarily subverted Alan’s control of the project. He had tolerated the ‘pilot’ policy on the understanding that the pilot would not detract from the full machine, but would become an integral part of it. If Huskey’s project failed, it would be a waste of time, and if it succeeded, it would lead to a marked change of plan. Naturally, Alan boycotted the development. Somehow Harry Huskey managed to scrape together enough equipment to make a start. His official role was ‘on the apparatus side’, and he was better at the form-filling; furthermore he did not need to think in terms of building the grand ACE installation, but only in terms of an experimental set-up. Jim Wilkinson and Mike Woodger joined in. Life in the Mathematics Division became very complicated, but they did learn something about electronics for the first time.

  At the same time, Alan managed to make a few experiments of his own in the cellar of Teddington Hall, the Mathematics Division building, and explained some electronics to Mike Woodger. He had devised circuits to transmit and receive pulses along a delay line, and a system to probe the circuit so as to examine the shape of the pulse on an oscilloscope. The NPL had nothing in the way of a machine to do this elementary engineering task, so, as at Hanslope, he had made one for himself. The whole thing43involved mounting four or five valves on a breadboard, and no more. He had no delay line to work with. A little later, coming back from lunch, he spotted a drainpipe lying in the long grass, and had someone help carry it back for him to try out as an air delay line. Don Bayley and ‘Jumbo’ Lee came and saw this ‘dog’s breakfast’ of an outfit in March or April 1947. Alan took Don for a walk round the grounds and complained bitterly of how he had been thwarted. Alister Watson, philosopher now turned radar expert, visited the NPL on business and heard Alan complain that ‘they say I don’t understand magnetism!’ Francis Price from Princeton days, whose family lived at Teddington, heard out his acrid comments on how the administration denied him the most standard pieces of equipment for experiment.*

  But these anarchic developments were overtaken by Darwin’s decision. He had become reconciled to the fact it would not be possible now, as it might have been during the war, to farm out the ACE to other organisations. Hitherto he had resisted setting up an electronics section within the NPL. But now it had become clear that there would be no single national computer, as had been expected in 1946, but various installations of which the NPL, if it was lucky, would have just one. His new plan was for a prototype to be constructed at the NPL, whereupon it would go to English Electric.

  This was a sound policy. The tenuous link with Wilkes was formally snapped on 10 April, and the Post Office contract cancelled. Instead, during the summer of 1947, a new Electronics section of the Radio Division was set up, under a certain H.A. Thomas.

  But these were two drawbacks to the new policy. The first was that Thomas’s interest lay in the industrial application of electronics, and not in computers. The second was that he had little knowledge of the use of electronics for pulse or digital techniques. It was not that he refused to make any concession at all to the ACE project, for indeed he very quickly produced a report (with which Womersley was ‘in full agreement’) on how a computer should be built. But this made little reference to the Turing scheme. Then Thomas imported some enormous cathode ray tubes from Germany. He intended them for use as digital display tubes. The staff from the ACE section dutifully went and stared at these, but with some amazement, for they seemed completely irrelevant to the plans for the computer.

  It was a curious sequence of events, in which the NPL administration had done everything possible to avoid ‘building a brain’. They had chased after Williams, although it would mean a complete redesign to use the kind of storage he was developing. They contemplated handing the construction to Wilkes, when he had only ‘a mechanic and a boy’ and incompatible design principles. They paid for Huskey to come over from America because of his experience ‘on the apparatus side’, and then failed to use it. Finally they had appointed, as the head of an electronics section, a man without motivation or experience for the job in hand. The one person whom they had not trusted was Alan Turing. The one policy they had not adopted was that of finding or training engineers to effect the proposals to which they had agreed in 1946. It was certainly not easy to find such expertise, but ultimately, they had not really tried.*

  After this happened, Alan withdrew. The programming work continued, and they went a long way with subroutines for floating-point arithmetic, including matrices and the numerical solution of differential equations. But Alan had lost interest in this work, although he spent time on what he called ‘abbreviated code instructions’. These took up the ideas announced in his original report, of having the computer expand its own programs. They made, in effect, a high level language for the computer, long before such things were developed elsewhere. But he was thinking more about the even higher level that he had announced in February, that of making a computer show intelligence. In this respect there was nothing to be gained by working at the NPL. Darwin and Womersley concurred in this opinion, and on 23 July Darwin wrote to the DSIR that since the ace had now reached the stage of ‘ironmongery’, it would be best if its designer were to ‘go off for a spell’. The separation of brain from hand could not have been made more explicit. It was agreed that Alan should spend a year at King’s to develop his theoretical
ideas. It was too early in his Civil Service career for this to be a normal ‘sabbatical year’, but the DSIR and the Treasury were persuaded to treat him as a special case.

  Monday 18 August 1947 was declared to be the official start to the building of the ACE. Darwin presided over a special morning meeting carefully calculated to impress upon the lowly engineers the privilege they enjoyed in working for Womersley’s project. There was much brave talk of taking on the Americans, and then Thomas ‘indicated the way in which he was about to approach the project in its initial stages’. Alan attended, but said nothing.

  Womersley, reporting to Darwin that the ACE should be complete by early 1950, was satisfied. In theory the ACE was still a venture of immense national importance, and Hiscocks had called this its ‘D-Day’. The truth, however, was that the NPL had now almost succeeded in cutting the ACE down to its own bureaucratic size. Only Alan Turing prevented the triumph being complete, awkwardly remaining to voice the original vision. On 30 August he wrote to Darwin that44

  A letter has come from Ministry of Supply …asking us to do their programming for them. This is work that we ought to be able to undertake, but it will not be possible with our present very small programming staff. This staff is quite inadequate for our own needs; it will have to be at least three times greater than it has been up to now, if we are to make a success of the ace project. The arrival of Mr D.W. Davies …will, of course, be of some help, but we need in addition another two or three bright [Scientific Officers] …immediately.

  It is essential to recruit the ace planning staff now, because it must be trained and in full production long before the machine itself is available for use. A large body of programming must be completed beforehand, if any serious work is to be done on the machine when it is made.

  In 1941 a direct appeal had worked wonders, but by 1947 the war might as well have never been. And talk of ‘planning staff’ for the universal machine was almost as unreal as it would have been in 1936. As it happened, the new recruit, Donald Davies, who came from atomic research, had been studying the abstract universal machine of Computable Numbers, rather annoying Alan by finding mistakes of detail in its construction. Alan had also given a talk on the ACE at the NPL which Rupert Morcom attended. The unhappy fact was that after eleven years there was still nothing but paper plans, a paper machine and paper programs, abstruse and insubstantial as the ‘satisfactory numbers’ he had tried to explain at the Clock House in 1936. He had given his all, and had nothing to show for it but paper. He would give them another chance to create the right conditions. But the wheels of 1939, that once had seemed to be turning in his direction, were now revolving backwards.

  In the summer of 1946 Alan had made contact again with James Atkins, who came to visit at Teddington. He had had a very different war, for standing fast as a conscientious objector he had spent four months in prison and then worked in the Friends Ambulance Unit. He asked Alan what he had done, and Alan replied ‘Can’t you guess?’ But James could only guess that it was to do with the atomic bomb. After the passage of nine years, they found that there was nothing that they could truly say or do. When James went, he left something behind, and returning after a few minutes caught Alan sitting in his bed-sitter with a particularly acute look of misery.

  Alan had mentioned The Cloven Pine to James, and in early 1947 Fred Clayton himself got in touch again. Alan replied on 30 May

  I was very glad to hear from you again, and should very much enjoy teaming up with you again for another sailing holiday.

  The best dates for me would be either the beginning of September or the beginning of July. The last year or two I have taken to running rather a lot. This is a form of compensation for not having been good at games at school. The application at present is that I have a Marathon race on August 23 and do not want to upset my training by sailing in August or late July.

  In the spring Alan had tried himself out against much stronger competition than that of the local suburban clubs. In the Southern Counties ten-mile championship of 22 February he had done ‘very badly’, but two weeks later at the National ten-mile event had come in sixty-second place out of three hundred runners. The Marathon race to which he referred brought out his endurance training to better advantage, and in fact he would come in fifth place.45 With a time of 2 hours, 46 minutes, 3 seconds he was only thirteen minutes behind the winner. Behind the off-hand words about ‘running rather a lot’, he had taken it very seriously. His letter to Fred continued with an equally off-hand reference to the war:

  I heard rumours at B.P. from time to time that you were coming there, and was disappointed that nothing came of it. You didn’t really miss anything.

  Alan went to Bosham at the end of June and fixed up a September holiday.

  Meanwhile on 3 August Alan’s father died at the age of seventy-three. He had been in poor health for several years. He left £400 more to Alan than to his brother, in compensation for the sum spent on John’s articled clerkship twenty years before. But Alan handed it over to his brother, not thinking this fair.* He also received his grandfather John Robert Turing’s gold watch. As it happened, Mr Turing died just twelve days before the passing of the British Raj ended that exile world to which he belonged. After his death Mrs Turing spoke little of him, and kept few reminders of his existence. Her own life was far from declining, and a new independence was reflected in the adoption of her second name Sara in preference to Ethel. She had also taken more interest in Alan’s doings, pleased that he was busy on something useful at last. She had sensed the high hopes of 1945, and sympathised with his complaints on how he had been thwarted.

  When Mountbatten relinquished British rule to the new Dominions of India and Pakistan, it was a belated victory of the new men. Another case of where the war had obliged the reforms long urged in the 1930s, it also represented the renovation of an independent British role in world affairs. But these were still uncomfortable days, in which the new world order was rapidly becoming apparent. The American loan, negotiated by Keynes before his death in 1946, and supposed to repair the British economy, had largely evaporated thanks to American insistence on making sterling convertible again. After a financial crisis, Dr Dalton withdrew convertibility on 20 August, pepping up the sagging team spirit on the radio: ‘God bless you all and your families. Get all you can of happiness and health and strength out of the sea air and then go all out in a great effort to help your country.’

  As usual the servants were being called upon to make up for the crimes and follies of the masters. Alan had probably had enough of this by now. But he and Fred Clayton took the advice regarding sea and fresh air, and had a holiday which recaptured something of the days of August 1939. Alan tended to be rather impatient with his friend’s handling of the boat, trying to explain feedback to him, and swearing mildly. But one day Fred took the helm over to the Isle of Wight, helped by a favourable wind, and all went well except that on the way back they bumped into a buoy and Alan said, without thinking, ‘I really ought to be a bit more careful with buoys.’ Then they both saw the joke and laughed.

  But it was no laughing matter. They exchanged their observations on the black market of unofficial truth, Fred contributing comments on the customs prevailing in India, where he had done low-level Japanese code-breaking, and Alan speaking of the war as a sexual desert (‘You didn’t miss anything’) except for the incident while in America. It then transpired that Alan had expected this holiday to hold something for him in that direction, which came as a shock to Fred, who explained that he was going to get married.

  Picking up the German threads after the war, Fred had entered into a warm correspondence with the sister of the two boys on whom The Cloven Pine was mainly based. It was she whom Fred intended to marry. It was an odd coincidence that one day, out on the water, Alan caught sight of a passing boat and said Oh, that’s rather awkward, it’s Martin Clarke’s sister, we were engaged.’ Joan recognised Alan, and waved and smiled. (She had seen him a few months before
at the LMS lecture.) But they did not meet. Alan told Fred of the broken engagement. Fred was left confused by his rejection of Alan whom, however, he did not find at all attractive. He and Alan talked about their respective decisions, ‘freedom and consistency of mind’ was not so easy for his friend, but Alan was now quite clear as to where he stood.

  On 30 September 1947 Alan resumed his King’s fellowship,* after a break of just under eight years from 2 October 1939. Because of the 1944 renewal, it was set to run until 13 March 1952. He was thirty-five, but could have, for not wearing a gown after dark. He had been taken for an undergraduate, and his youthfulness surely accentuated what was something of a return to the life of the past. In certain ways, of course, Cambridge had changed. Most students were in their mid-twenties, and had arrived after some years of service life rather than with the artificial immaturity of public schools. It was a more personally ambitious, less politically conscious Cambridge than that of the 1930s. But no one spoke of the war, which was fading like a dream, and it would take more than the war to change the special character of Kings.

  One friend immediately stood out from the rest. Robin Gandy had taken Part III of the Mathematical Tripos that summer, and was now working in theoretical physics towards a fellowship. Soon after term began, Robin called on Alan and asked if he could borrow his copy of Eisenhart’s book on continuous groups. Alan took it off the shelf, and out fluttered a newspaper picture of a rank of pageboys at Princess Elizabeth’s wedding. There was someone else in the room, probably Robin’s physicist friend Keith Roberts, and Alan only said darkly ‘You’ll find nice pages like that in my books.’ But next morning, Alan said to him, ‘We know each other quite well now …I might as well tell you that I am a homosexual.’ Robin’s own personality was different, but he was someone who like Alan cared that (as Carpenter had put it)46