Alan Turing: The Enigma The Centenary Edition

by Andrew Hodges

  In this respect, however, development was very far from speedy. There was an overwhelming problem with the ACE project. This was that although the ν PL had a Radio Division, it did not have a single electronic engineer capable of appreciating, let alone implementing, Alan’s ideas. Back in December 1944, Womersley had told the Executive Committee that plans for new machines ‘could be put into effect only by cooperation between the Division and certain industrial organisations – possibly along the lines of extra-mural development contracts.’ But no progress had been made towards making this cooperation possible. There was one solid medium-term possibility, that of having English Electric, a firm with which Darwin had connections, manufacture a machine to commercial standards. Its director, Sir George Nelson, had attended the March meeting. But it was not at all clear who was to do the immediate development work. This was no small impediment to the confident hope expressed in Alan’s report of being able to produce the equipment for the logical control within six months.

  A further problem lay in the internal structure of the NPL. At Hanslope, Alan had worked happily with Don Bayley, putting their different kinds of skill together. In this respect the Delilah project had been practice for the ACE, for he would have liked to work in much the same way again, if on a larger scale. (He had vaguely suggested that Don himself should come to the NPL, but Don was not due for release until February 1947, and he also felt he was rather more than the ‘amplifier king’ that Alan said he would need.)

  But the National Physical Laboratory did not encourage any such ad hoc, informal collaboration. Its division of labour drew a firm line between brain and hand. Alan was cast firmly in the role of the theoretical designer, and was not expected to know anything about practical engineering. The bureaucratic outlook of the NPL also showed in the form-filling and permission-seeking necessary for the requisition of equipment, Meanwhile, to make matters worse, the post-war chaos, presenting something akin to a black market in war surplus materials, called for the skills of the spiv in locating hardware of any kind. For these reasons, there was no immediate prospect of having engineers qualified to build the circuits, and there was no facility for Alan to conduct practical experiments himself.

  There was a more general difficulty facing the ACE project. It was one analogous to the arrival of the Enigma information in 1940. Alan had poured out a decade’s worth of ideas into the lap of an organisation which had not been noted for innovation. In 1940 the cryptanalysts had naively expected that the government could take the deciphered messages and put them to good effect. In fact it had needed two years of painful adjustment before this could be done, even with all the pressure of war. Now again the cornucopian abundance of the ACE design would require a change in attitudes. But there was no precedent for it, and although the administrators talked knowingly about what was needed, they had no clear idea of how to proceed. There was no tradition of major innovation at the NPL, and the ACE project brought out the conservative and negative character of the institution. Just as in 1941, Alan was impatient and uncomprehending of the organisational inertia.

  Nor, perhaps, did he appreciate that the very high priorities enjoyed by Bletchley, and the willingness of other organisations to sacrifice their independence, could no longer be expected in 1946. Thus at Dollis Hill, while there was no question about the competence of the Colossus engineers, their director, Radley, did not attach great importance to the work being done on delay lines for the ν PL. The Post Office had manifold tasks of its own in connection with the wartime backlog, and there was now no higher authority, no national policy, to coordinate the priorities of the various state enterprises. Alan and Womersley made an official visit to Dollis Hill on 3 April 1946, and thereafter work began – but in a desultory way, with the effect of creating an unforeseen delay, and a sense of uncertainty as to direction.

  Alan had written in his report about the possibility of using cathode ray tubes as a quite different kind of storage system, and it was probably at his prompting that on 8 May 1946 Womersley wrote to TRE with an enquiry about the state of research at the radar establishment into the use of such tubes for storage, explaining that it might ‘form a suitable alternative to, or possibly even an improvement on, the mercury delay line which we are at present intending to use in our automatic computing engine .. V The response was not unhelpful, and on 13 August Darwin was able to write to Sir Edward Appleton at the DSIR:10

  …As I told you Womersley was down at TRE to see whether they could do any work about the ACE machine. He tells me that it looks a most promising chance, and I think we should go ahead on it. Their lay-out for the job looks good, and I gather it appealed strongly to F.C. Williams as a job he would like to do, so that it should get a good chance. I am kicking myself for not having thought of it months ago as a possibility.

  As to what comes next Womersley has got to use some tact in exploring how we stand with the Post Office who have started to give us help, which would be very good but that they are not in a position to plunge very deep. It will also be necessary to square TRE officially over priorities, and on this I should like to bring high power to bear if necessary, because we have got a splendid chance of jumping in ahead of America.

  F.C. Williams was one of the top electronic experts at TRE, and he was enthusiastic not because he was interested in computing, which he was not, but because he was anxious to find peacetime applications for the electronic skills developed in wartime radar. In finding such applications he had a mind of his own, and had an option open to him that did not accord with Darwin’s ‘high power’. It derived from Manchester.

  Newman had left Bletchley to become Professor of Pure Mathematics at Manchester University, taking Jack Good and David Rees with him as junior lecturers. (Rees was another of the 1939 Part III class, who had joined Welchman’s hut in December 1939, and later joined the Newmanry.) In moving from a Cambridge lectureship to a Manchester University chair, he was following Blackett, then Professor of Physics. Together they constituted a formidable team, and one which did not see why Darwin should monopolise electronic computers. As the first reader of Computable Numbers and the co-author of the Colossus, Newman appreciated the potential of computers as well as anyone, and if he lacked Alan’s emotional thrust towards ‘building a brain’, and the experience of assembling components himself, he compensated with a greater skill in the art of the possible.

  Writing to von Neumann11 on 8 February 1946, Newman had explained that he was

  hoping to embark on a computing machine section here, having got very interested in electronic devices of this kind during the last two or three years. By about 18 months ago I had decided to try my hand at starting up a machine unit when I got out. It was indeed one of my reasons for coming to Manchester that the set-up here is favourable in several ways. This was before I knew anything of the American work, or of the scheme for a unit at the National Physical Laboratory. Later I heard of the various American machines, existing and projected, from Hartree and Flowers.

  Once the NPL project was started it became questionable whether a further unit was wanted. My view was that in this, as in other branches of technology, basic research is wanted, which can go on without worrying about getting into production …

  Newman’s intention was that

  mathematical problems of an entirely different kind from those so far tackled by machines might be tried, e.g. testing out (say) the 4-colour theorem or various theorems on lattices, groups, etc. …

  He explained that

  Anyhow, I have put in an application to the Royal Society for a grant of enough to make a start. I am of course in close touch with Turing. After discussion with him, and hearing Hartree and Flowers, it seemed to me that if we start on ‘mathematical’ problems here, in the above sense, we ought to be able to manage with considerably less storage, though I have asked to the Royal Society to be prepared for something fairly substantial.

  Newman’s application was for a grant to cover the capital cost and fiv
e years of salaries for an electronic computer.12 The Royal Society set up a committee to investigate the application for a grant, consisting of Blackett, Darwin, Hartree, and two pure mathematicians, Hodge from Cambridge and Whitehead from Oxford. Darwin opposed it on the grounds that the ACE was to serve the needs of the country. Womersley had expressed the particular fear that Newman would steal Flowers away from the ACE. But he was outvoted, for it was approved that there should be ‘a different type of machine’ for Newman’s project. On 29 May the Treasury allocated £35,000 to Newman. The rationale was that as ‘fundamental science’, his proposal fell into the orbit of the Royal Society, and did not conflict with the DSIR. It meant that a rather surprising breath of mathematical innocence was felt again, with a computer development not required for weaponry.

  It so happened that Blackett knew F.C. Williams from before the war, when they had collaborated on an automatic curve-tracer for the differential analyser. Both Darwin and Newman, therefore, were looking to Williams to help them ‘jump in ahead of America’, and Darwin’s plan for a single national computer installation had already been undermined. The question of who was going to build the ACE remained unresolved while Williams decided between these suitors.

  This incipient rivalry was further complicated by the fact that a third British electronic computer project was initiated in mid-1946. This was the brainchild of M.V. Wilkes, Alan’s fellow ‘B-star’ of 1934 who in 1945 had left wartime work at TRE to resume his position at the Mathematical Laboratory in Cambridge, of which he now became director. He was in touch with Womersley at once, but the ENIAC and EDVAC plans were secret until the spring of 1946, and only then could Hartree tell him about what he had seen in 1945. Hartree then also arranged for him to attend a course of lectures arranged by the ENIAC team at Philadelphia in July and August 1946.

  This course at the Moore School, together with the reports issued by von Neumann’s group at the IAS, enjoyed very considerable influence upon the future development of computers. For one thing, it brought about the first federal funding for a machine on the lines of the EDVAC. A certain James T. Pendergrass represented the Navy’s CS AW, and reported back13 upon the virtue of a universal machine, as opposed to the special purpose equipment which had ‘often proved to be expensive and time-consuming.’ (Presumably Travis had been given the same analysis a year earlier.) For another, it inspired Wilkes with great enthusiasm for putting his wartime electronic experience to work in building a British version of the EDVAC.

  Alan, in contrast, remained unaffected by the American developments, and they by him. In growth as in conception they were independent. There was a little indirect contact between the ν PL and the American group. Hartree had made a visit to the ENIAC in the summer of 1946, being allowed to use it himself, and took with him a copy of the ACE report and a ‘third version’ of the ACE design.14 But its programming ideas made no obvious impression upon the Americans.

  As a theoretician of computers, von Neumann had been joined by Norbert Wiener, the American mathematician of a slightly earlier generation, whom the war had likewise taken from group theory to machinery, although in his case the servo-mechanisms of anti-aircraft artillery had been the formative influence. Thus von Neumann and Wiener corresponded in connection with the potential of the planned EDVAC, but mostly in terms of the faculty of conditional branching corresponding to ‘feedback’. They did not discuss hierarchies of programs, nor the computer reorganising and creating its own instructions. They remained most impressed with the McCulloch and Pitts ideas, which suggested that the logical functions of electronic valves bore some similarity to the structure of neurons in the human nervous system. In a letter15 of 29 November 1946, von Neumann wrote to Wiener of the ‘extremely bold efforts’ of Pitts and McCulloch, with which he ‘would like to put on one par the very un-neurological thesis of R. [sic] Turing.’

  In the other direction, likewise, there was limited communication. The Draft Report on the EDVAC was there at the NPL, and Alan continued to make use of its notation for logical networks. David Rees, who attended the Moore School lectures on behalf of the Manchester interest, reported back to Alan and Jim Wilkinson for ten days or so. But the American plans had no particular influence on the ACE project, Alan being notably sceptical about the prospects for the Iconoscope, the storage medium on which the Americans were pinning their hopes. They did not think of the American development as a rival; it was simply another project. The ACE was Alan Turing’s own thing, like naval Enigma, like the Delilah. It was not, however, developing in quite the same way.

  Although the wartime spirit lived on amongst the huts and bombsites of 1946, the ACE section did not flower with the camaraderie of Hut 8, or the quite remarkable rapport that Alan had established with Don Bayley. Mike Woodger came back from sick leave in September and found a note on his desk asking him to program BURY and UNBURY. The relationship continued in this master-and-servant way. Alan liked the earnest, rather nervous Mike Woodger, and tried to be kind, but hid it under what appeared as an abrupt, rather frightening manner. He probably did not realise the awe with which he was regarded by young people like Mike Woodger, just starting on a career. Always casting himself as the Young Turk embattled against officialdom, he still found it hard to see himself as the official in others’ eyes. He was impatient of slowness, and could not use his imagination to make communication more effective.

  Jim Wilkinson was older and more experienced than Mike Woodger, but he too found many days when it was better to keep out of the way of the now somewhat isolated ‘creative anarchy’ that was Alan Turing. ‘Likeable, almost lovable …but some days depressed’, he appeared; his mercurial temperament and his emotional attitude to his work showing clearly. It was at about this time that Alan got the long-promised promotion to Senior Principal Scientific Officer, and he took Jim Wilkinson and Leslie Fox from Goodwin’s department out to a celebration dinner in London. The train journey was spoilt by a sultry row over some mathematics, and then, as they arrived at Waterloo, the clouds cleared and he was buoyant again.

  This particular argument arose because Alan had become involved in a problem of numerical analysis, the work done in Goodwin’s section. In 1943 the statistician H. Hotelling16 had analysed the procedure for solving simultaneous equations (or, roughly equivalently, for inverting a matrix) and his result made it appear that errors would grow very rapidly as successive equations were eliminated. If this were so it would undermine the practical usefulness of the ACE. Goodwin’s section, being directly concerned with the problem, had attacked it heuristically in 1946 by solving a set of eighteen equations that had come up in an aerodynamic calculation, and Alan had joined in (notably the least competent at the detailed work), on the desk machine exercise. To their surprise, they found the final errors to be remarkably small. Alan had undertaken a theoretical analysis of why this should be. It was a typical Turing problem, needing a fresh attack, and with a concrete application. He tackled it much as he had developed a theory of probability for use at Bletchley.

  This work of course, did not lie far in the past, and he set Mike Woodger some probability problems, including the one about the ‘barrels of gunpowder’. There was also professional contact arising out of wartime work. Jack Good and Newman had made a visit to the ν PL – Newman, of course, being interested in setting up his Manchester computer project – and Jack had managed to disprove Alan’s assertion that no one could write an instruction table that was free from error at the first attempt. Jack Good had also written a short book17 on Probability and the Weighing of Evidence, effectively setting out the theory they had employed at Bletchley, though not its more advanced applications. The ‘sequential analysis’ method was, as it happened, soon published in America by the statistician A. Wald,18 who had developed it independently for the testing of industrial components. Alan, in contrast, published nothing that came of his Bletchley work, except in the less direct sense that almost everything he was doing was flowing from his wartime experi
ence added to his pre-war theory of machines.

  Rather than forming new ties of friendship at the ν PL, he retained those of the war. Donald Michie, now an undergraduate at Oxford, was one of these friends, and a footnote on Alan’s October 1946 letter to Jack Good, with comments on the draft of his book, noted cryptically that ‘Donald has agreed to help and I have now got the necessary gadgets for the treasure.’ This was a reference to a proposed expedition to recover the silver bars. (David Champernowne had meanwhile realised a healthy profit in his ingots, which had remained safely in his bank.) There had been a previous attempt with Donald Michie, who was offered the choice of either a one-third share of the total proceeds or a payment of £5 per expedition. This was itself a nice example of the Turing theory of probability, which appealed to the odds that a perfectly rational person would be prepared to bet on an event. As a perfectly rational man, Donald Michie opted for the latter choice. The first real-life treasure hunt had been a failure, since when they went to the wood near Shenley where one bar was buried, Alan found that the landmarks had changed since 1940, and he could not locate the spot. The point of the ‘gadget’ was that it was a metal detector which Alan had designed and built himself. On the second trip, it functioned, though only to a depth of a few inches. It successfully located a great many pieces of metal under the surface of the wood, but not the silver bar. As for the second bar, he knew where that was, but they found that they were unable to apply the UNBURY routine when standing in the bed of the stream.

  Such failures he would easily laugh off. This was not his only visit back to Buckinghamshire, for he spent a weekend, probably in December 1946, discussing D. Gabor’s new theory of communication19 with Don Bayley. This time he distinguished himself by fainting when he grazed himself shaving. He had told Don long before about this reaction to blood, but this was the first time Don had seen it happen. There had also been an occasion in October 1945, when he, Don Bayley, Robin Gandy and ‘Jumbo’ Lee met up to go to a lecture on wartime radio work at the Institute of Electrical Engineers. Afterwards they had gone to Bernard Walsh’s oyster restaurant and rather hoped to be fed on the house – in which they had been disappointed. Alan had cycled into London from Teddington and had parked his bicycle outside the Soho restaurant, from which it was duly stolen.