imitation game movie

Noel Chiappa jnc at
Tue Feb 10 12:31:07 CST 2015

    > From: Jon Elson

    > such as to not evacuate Coventry when they knew it was next for getting
    > blitzed.

Ah, this is alas an urban legend ('bogo-meme', to coin a nice neologism);
started, IIRC, by Winterbotham.

This has been demolished, by, among others, R. V. Jones, who was in a
position to know (as the recipient of Ultra material at the Air Ministry), in
his biographical work, "The Wizard War", pp. 147-151. He refers to evidence
given by John Martin (Churchill's secretary, who was with him in the car that
night), and John Colville (Assistant Private Secretary, who was on duty at 10
Downing St. that night). They are both quite clear that the target was
unknown before the raid started; Jones gives the details on why not.

    > there are some descriptions that the actual wiring of the rotors was
    > done AT Bletchley

I'd love to read about that - do you know/recall where you saw it?

    > If a German spy was to get his hands on the drawings for even one
    > (wired) rotor, they would have realized how thoroughly the British had
    > penetrated the Enigma system

I am less certain of this. I seem to recall (alas, too busy to look it up,
unless someone's really interested) that the Germans had something of a
modern concept of code security, where it's assumed that the actual ciphering
machine is compromised, and security depends on the security of the keys.

Given the wide deployment of Enigma at the tactical level, the odds were good
that the machine itself had been compromised. So for them to have found out
that the British had the rotor wiring would not have been a big surprise, I
would expect.

However, had they gotten any kind of detailed description of the Bombe, it
would have not been that hard to work out that its use was to break into
Enigma. In that sense, the Bombe's overall design was in fact a bigger secret
than the fact that they had the rotor wiring.

And of course as a result of the XX system, the British were fairly sure that
there were no German spies in the UK at the time, anyway.


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