Historical question: Longevity of Colossus.

[Brian Randell]

Hi:

At 5:48 pm +0100 2/8/99, Quentin Campbell wrote:
>On Mon, 2 Aug 1999, Paul Leyland wrote:
>
>> My question: why did GCHQ keep *two* of them for so long?  If they only had
>> one, it could have been an exhibit in a museum.   Keeping two bits of kit,
>> each occupying several cubic meters and requiring 5.5kW of power to run
>> suggests that they were still useful.
>>
>> Does the answer to this question have any relation to the observation that
>> the design of Colossus was classified until very recently?
>>
>>
>> Paul
>
>Brian Randell is probably among the best placed on this list to help
>answer that.
>
>A couple of things I recall from talks given here:
>
>1. At the end of the War, Donald Michie and others tried "programming"
>   a Colossus to do some non-cryptographic computations. I also understand
>   it was tried on some cryptographic tasks for which it was not
>   originally designed. It may be it had some utility in these other areas
>   that extended its useful life.
>
>2. Tony Sale has also said that there are some analysis algorithms that
>   are built into the logic of Colossus and which could be selected as
>   part of its set-up menu that remain classified still. He was told
>   that some of these techniques were still in use at Cheltenham until
>   fairly recently.

I'm afraid I've nothing much to add to Quentin's comments. When, in
lectures years ago about my historical investigation into the Colossus, I
was asked: "Why is is still partly classified?" I learnt to answer: "The
more appropriate question is why is it now partly de-classified - after all
Britain's World War I codebreaking activities are still completely
classified."!

(The answer to this alternative question is I think largely bound up with
the change from Ted Heath's Conservative government to Harold Wilson's
Labour one - which was more sympathetic to the argument that Britain's
code-breaking achievements, and the contributions of the already very
elderly scientists and engineers who made them possible, should be made
known, given that all sorts of misleading stories were being published.)

Now, when questions arise about Colossus I refer people to Tony Sale, who
is far more expert and knows much more about the subject than I do.

Cheers

Brian Randell



Dept. of Computing Science, University of Newcastle, Newcastle upon Tyne,
NE1 7RU, UK
EMAIL = Brian.Randell@newcastle.ac.uk   PHONE = +44 191 222 7923
FAX = +44 191 222 8232  URL = http://www.cs.ncl.ac.uk/~brian.randell/