Turing's detailed computer scheme was drawn up in a continuation of wartime spirit: as a plan that could be effected immediately with the memory storage (cumbersome acoustic delay lines, as used in radar) that was to hand. Turing knew that superior technology would soon transform design: his emphasis was on speed in every sense, and in the exploitation of the universal machine concept. This meant, in particular, implementing arithmetical functions by programming rather than by building in electronic components, a concept different from that of the American-derived designs.
The hardware design was short-term; but his prospectus for the use of the machine was visionary. Turing projected a computer able to switch at will from numerical work to algebra, codebreaking, file handling, or chess-playing. Methods for handling subroutines included a suggestion that the machine could expand its own programs from an abbreviated form, ideas well ahead of contemporary American plans.
A later talk (February 1947) depicted a national computer centre with remote terminals, and the prospect of the machine taking over more and more of its own programming work. In 1947 his Abbreviated Code Instructions marked the beginning of programming languages. But not a single component of the ACE was assembled, and Turing found himself without any influence in the engineering of the project. The lack of cooperation, very different from the wartime spirit, he found deeply frustrating.
From October 1947, the NPL allowed, or perhaps preferred, that he should spend the academic year at Cambridge. Rather than publish these fundamental principles of computing, he spent his time on new study amidst the post-war renaissance of science, not in mathematics or technology but in neurology and physiology. Out of this came a pioneering paper on what would now be called neural nets, written to amplify his earlier suggestions that a sufficiently complex mechanical system could exhibit learning ability. This was submitted to the NPL as an internal report, and never published in his lifetime. Meanwhile the NPL made no advance with the construction of the ACE, and as Turing's position fell back, other computer projects at Cambridge and Manchester took the lead.
Indeed it was Newman, who had been the first reader of On computable numbers, and in charge of the electronic breaking of the 'Fish' ciphers, who was partly responsible for this. On his 1945 appointment to the chair of pure mathematics at Manchester University, he had negotiated a large Royal Society grant for the construction of a computer. Newman strongly promoted Turing's principle of the stored-program computer, but unlike Turing, intended no personal involvement with engineering. He conveyed the basic principles to the leading radar engineer F. C. Williams, who had been attracted to Manchester, and the latter's brilliant innovation made possible a rapid success: Manchester in June 1948 had the world's first practical demonstration of Turing's computer principle.
Although losing in the race to implement a universal machine, and slow to communicate or compete in the game of scientific priority, Turing ran very competitively in a literal sense. After the war he developed his strength in cross-country running with frequent long-distance training and top-rank competition in amateur athletics. He would amaze his colleagues by running to scientific meetings, beating the travellers by public transport, and only an injury prevented his serious consideration for the British team in the 1948 Olympic Games.
The return to Cambridge helped Alan Turing form an agreeable circle of lasting friendships, particularly with Robin Gandy, who began at this period to develop under Turing's influence and would later inherit his mantle as a mathematical logician. Although never secretive about his sexuality, he now became more deliberately outspoken and exuberant, and all thoughts of comfort or conformity were now left behind. A mathematics student at King's College, Neville Johnson, became a lover.