176 | 17 UlTRA REVElATIONS
No mention was made of Alan Turing, or any of the others who I had learned were involved
with Bletchley’s code-breaking machines.
A further, even more sensational, book Bodyguard of Lies^3 then revealed more about how the
Germans had been using Enigma cipher machines. It gave some information about the work
of first the Polish cryptanalysts, and then of Turing and others at Bletchley Park on a machine
called the ‘bombe’ that was devised for breaking Enigma codes, but made no mention of com-
puters and referred to electronics only in connection with radar and radio. Its main topic was
the immense impact of all this work on the Allies’ conduct of the war.
Emboldened by what seemed to be a rather significant change in government policy con-
cerning any discussion of Bletchley Park’s activities, I made some enquiries as to whether
another request to declassify the Colossus project might now have a chance of being treated
favourably. I was strongly urged not to write to the Prime Minister again—apparently my earl-
ier request had caused considerable waves on both sides of the Atlantic. Instead, on the advice
of David Kahn, I wrote on 4 November 1974 to Sir Leonard Hooper, described by Kahn as
being the former head of the Government Communications Headquarters (GCHQ), who was
by then an Under Secretary in the Cabinet Office with, I believe, the title of Coordinator for
Intelligence and Security. After a brief exchange of correspondence, I received a letter from Sir
Leonard dated 22 May 1975 with the welcome news that ‘approval had been given for the release
of some information about the equipment’, and that it was proposed to release some wartime
photographs of Colossus to the Public Record Office. I was invited to come to London for dis-
cussions at the Cabinet Office.
This visit occurred on 2 July 1975. When I arrived, somewhat nervously, in the Cabinet Office
building I was escorted along a corridor, past what I was told was the famous internal doorway
that provided a discreet means of gaining access to 10 Downing Street, to a panelled room
where I met Sir Leonard Hooper, his personal assistant, and Dr Ralph Benjamin. (I do not recall
whether it was then or later that I learned that Dr Benjamin was Chief Scientist at GCHQ.) I was
shown the photographs, and we discussed in detail the wording of the explanatory document.
(Their concern was that some of the wartime terminology used in their explanation might not
be understood by present-day computer people.) We readily agreed on some modest rewording
of the one-page document.
I was then told that the government were willing to facilitate my interviewing the people
who had led the Colossus project after they had been briefed as to just what topics they were
allowed to discuss with me—this was with a view to my being allowed to write a history of the
project, provided that I would submit my account for approval prior to publication. Needless to
say, I agreed. My assumption was that the fact that I was viewing the Colossus solely from the
viewpoint of the history of computing, and that I had little interest in (and less knowledge of )
cryptography, contributed to the decision to facilitate my investigation.
The photographs and explanatory document were made available at the Public Record Office
(now The National Archives) on 25 October 1975, and I had the pleasure of sending a letter
(now on display in the Turing Exhibition at Bletchley Park) to Mrs Turing, saying:
I thought you would like to know that the Government have recently made an official release of
information which contains an explicit recognition of the importance of your son’s work to the
development of the modern computer. They have admitted that there was a special purpose
electronic computer developed for the Department of Communications at the Foreign Office
in 1943. Their information release states that Charles Babbage’s work in the 19th century and