Footnotes

• 'MY DUTIES ARE ALMOST ENTIRELY CONCERNED WITH THE USE OF THE ELECTRONIC COMPUTERS... ONE CAN MAKE THESE MACHINES DO ALMOST ANYTHING ONE WANTS' – Alan Turing works on developing the prototype of the modern computer. The theoretical concept of the Universal Turing Machine envisaged a single machine engineered to receive a multiplicity of programmes as opposed to a machine engineered for a specific purpose (such as the German Enigma): 'the universal Turing machine is now seen to embody the principle of the modern computer: a single machine which can be turned to any task by an appropriate program' (Andrew Hodges, ODNB).
  
  Turing had been appointed Deputy Director of the Manchester Computing Laboratory in October 1948 by Max Newman. Newman had already installed at Manchester the so-called Small Scale Experimental Machine (better known as the 'Manchester Baby'), which had been running programmes from that June. This is generally recognised as being the world's first stored-programme electronic computer and the first practical realization of the Turing's Universal Machine. From this was developed the Manchester Mark 1, or Manchester Automatic Digital Machine, work on which had begun in August 1948. This is presumably the machine "made by the Engineering Dept of rather Heath Robinson type" referred to in our letter. It had been operational since April 1949. By October 1949 it was ready, bar some details, for Ferranti to manufacture; while the prototype remained at Manchester. The Ferranti Mark 1 (also known as the Manchester Electronic Computer or Manchester Ferranti) is generally recognised as being the world's first commercially-available electronic stored-program computer. The first model off the production line was to be installed at Manchester in February 1951. It was on this machine that Turing worked on the mathematical theory of morphogenesis, the theory of growth and form in biology (so his garden did, indeed, keep him busy). Ferranti had intended to display one of the Mark 1 computers at the Science Museum during that year's Festival of Britain, as Turing tells Eperson, but this proved impossible; so they displayed instead a single-purpose games machine called the Nimrod. (Turing paid a visit to the exhibition, had a game of Nim and beat the machine.)
  
  The letter's recipient, Canon Donald Eperson, had been Turing's mathematics teacher at Sherborne School, where he had been a sympathetic mentor (as this letter indicates). In Hodges's words: 'Eperson, just a year down from Oxford and a gentle, cultured person, the kind of master who would constantly be played up by the boys. Here was the chance for the school to redeem itself at last, the spirit breaking through the letter of the law. And in a negative way, Eperson did what Alan wanted, by leaving him alone... He found that Alan always preferred his own methods to those supplied by the text book, and indeed Alan had gone his own way all the time, making few concessions to the school system' (Alan Turing: The Enigma, 2014 edition, p.43). Robin Gandy, who is also mentioned in this letter, was Turing's great friend and pupil, and it was to him that his mathematical books and papers were bequeathed.
  
  Eperson instilled in Turing a love of Lewis Carroll, and had compiled a Lewis Carroll Puzzle Book, a second edition of which came out in November 1949. This provides a terminus post quem for dating the letter (acquired from Eperson by the present owner). A further clue is furnished by the fact that Turing moved to Hollymeade in the summer of 1950 (Alan Turing, p.537). He was at this period working on his famous paper 'Computing Machinery and Intelligence', published in the October 1950 issue of Mind, in which he outlines what has since become known as the Turing Test (as well as giving details of the Manchester machines that feature in our letter).