Table Of ContentALAN TURING: THE ENIGMA
THE BOOK THAT INSPIRED THE FILM
THE IMITATION GAME
Andrew Hodges is Tutor in Mathematics at Wadham
College, Oxford University. His classic text of 1983,
since translated into several languages, created a new
kind of biography, with mathematics, science, com-
puting, war history, philosophy and gay liberation
woven into a single personal narrative. Since 1983
his main work has been in the mathematics of
fundamental physics, as a colleague of Roger Penrose.
But he has continued to involve himself with Alan
Turing’s story, through dramatisation, television
documentaries and scholarly articles. Since 1995 he
has maintained a website at www.turing.org.uk to
enhance and support his original work.
TO THEE OLD CAUSE!
The dedication, epigraphs and epitaph, are taken
from the Leaves of Grass of Walt Whitman.
‘Alan Turing was by any reckoning one of the most remarkable
Englishmen of the century. A brilliant mathematician at Cambridge
in the ’30s, Turing discovered that his was precisely the kind of
intelligence needed by Britain during the war and became the
presiding genius at Bletchley Park, the boffin centre which cracked
the German Enigma code. (A character in McEwan’s The Imitation
Game was loosely based on him.) There he became obsessed by the
notion of machine intelligence and was, in effect, the father of the
modern computer. Mistrust and bureaucracy, however, frustrated
many of his plans after the war, when Turing was to discover that
though he was the master of his own sphere, politically he remained
as he was in 1941 – a servant. A homosexual, Turing found his own
morality and scientific ideas increasingly at odds with the values
of the state which he served. Eventually, he committed suicide.
Andrew Hodges’s book is of exemplary scholarship and sympathy.
Intimate, perceptive and insightful, it’s also the most readable
biography I’ve picked up in some time’
Richard Rayner, Time Out
‘Researched and written extraordinarily well. It is a first-class contri-
bution to history and an exemplary work of biography’
Nature
‘Life and work are both made enthralling by Hodges, himself a
scientist’
Sunday Times
‘This rather shadowy figure has now finally been lifted into the light
of day . . . it has to be said that Andrew Hodges has put together an
extraordinary story’
Sunday Telegraph
‘This book has a great deal to offer: clear technical descriptions set
against their backgrounds; the story of a man largely at odds with
the system he lived in; and the puzzle of Alan Turing himself’
Times Higher Education Supplement
‘Andrew Hodges, in this fine biography Alan Turing: The Enigma,
brings Turing the thinker and Turing the man alive for the reader
and thus allows us all to share in the privilege of knowing him’
Financial Times
‘This is not a book to be argued about. It is a book to be read’
New Scientist
‘A major work at any level. Recommended’
Personal Computing World
‘An almost perfect match of biographer and subject…. [A] great
book.’
Ray Monk, Guardian
‘A captivating, compassionate portrait of a first-rate scientist who
gave so much to a world that in the end cruelly rejected him. Per-
ceptive and absorbing, Andrew Hodges’s book is scientific biogra-
phy at its best.’
Paul Hoffman, author of The Man Who Loved Only Numbers
‘A remarkable and admirable biography.’
Simon Singh, author of The Code Book and Fermat’s Enigma
ANDREW HODGES
Alan Turing:
The Enigma
The Book That Inspired the Film
The Imitation Game
Princeton University Press
Princeton and Oxford
Published in the United States by Princeton University Press
41 William Street, Princeton, New Jersey 08540
Publipsrheesds. pbryi nVcienttoang.ee d2u014
2 4 6 8 10 9 7 5 3 1
Copyright © Andrew Hodges 1983
Preface copyright © Andrew Hodges 2014
Andrew Hodges has asserted his right under the Copyright, Designs
and Patents Act 1988 to be identified as the author of this work
This book is sold subject to the condition that it shall not,
by way of trade or otherwise, be lent, resold, hired out,
or otherwise circulated without the publisher’s prior
consent in any form of binding or cover other than that
in which it is published and without a similar condition,
including this condition, being imposed
on the subsequent purchaser
First published by Burnett Books Ltd
in association with Hutchinson Publishing Group 1983
Unwin Paperbacks edition 1985
Reprinting 1985 (twice), 1986, 1987 (twice)
First published by Vintage in 1992
This edition published inV tinhtea Ugen ited Kingdom in 2014 by
Random House, 20 Vauxhall Bridge Road,
Vintage
London SW1V 2SA
Random House, 20 Vauxhill Bridge Road,
A PenguinL Ronadnodno mSW H1oVu s2eS CAompany
A Penguin Random House Company
Library of Congress Control Number: 2014952514
ISBN: 978-0-691-16472-4
Pwriwnwte.dv ionnta agcei-db-ofroekes .pcaop.uerk. ∞
Addresses for companies within The Random House Group Limited
can be foPurnindt eadt: iwn wthwe .Urannidteodm Shtoatuesse .ocfo A.umk/eorficfiaces.htm
The Random Hou1s e3 G 5r 7o u9p 1 L0i m8 i6te 4d 2Reg. No. 954009
A CIP catalogue record for this book
is available from the British Library
ISBN 9781784700089
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Contents
List of Plates ix
Foreword by Douglas Hofstadter xi
Preface xv
PART ONE: THE LOGICAL
1 Esprit de Corps to 13 February 1930 3
2 The Spirit of Truth to 14 April 1936 60
3 New Men to 3 September 1939 141
4 The Relay Race to 10 November 1942 202
BRIDGE PASSAGE to 1 April 1943 305
PART TWO: THE PHYSICAL
5 Running Up to 2 September 1945 325
6 Mercury Delayed to 2 October 1948 394
7 The Greenwood Tree to 7 February 1952 491
8 On the Beach to 7 June 1954 574
Postscript 665
Author’s Note 666
Notes 680
Acknowledgements 714
Index 715
List of Plates
1 Alan’s father, Julius Turing (John Turing)
A lan Turing with his brother John, St Leonard’s, 1917
(John Turing)
Alan with his mother in Brittany, 1921 (John Turing)
2 C olonel and Mrs Morcom with Christopher, 1929
(Rupert Morcom)
Alan Turing with two school contemporaries, 1931
(Peter Hogg)
Alan Turing in 1934 (John Turing)
3 Alan Turing with his parents, 1938 (John Turing)
Sailing at Bosham, 1939 (John Turing)
4 The naval Enigma machine
5 A Colossus machine in operation at Bletchley Park, 1944–5
(HMSO)
The Delilah terminal, 1945 (HMSO)
6 Robin Gandy in 1953 (Robin Gandy)
F inish of a three-mile race, possibly 1946 (King’s College,
Cambridge)
The Pilot ACE computer in 1950
7 The prototype Manchester computer, 1949 (Department
of Computer Science, University of Manchester)
A lan Turing at the console of the Ferranti Mark I computer,
1951 (Department of Computer Science, University of
Manchester)
8 A lan Mathison Turing, Fellow of the Royal Society, 1951
(King’s College, Cambridge and The Royal Society)
