184 | 18 DElIlAH—ENCRyPTING SPEECH
have forbidden Turing’s involvement. During this time Turing also acted as consultant to the
engineers who were designing an electronic version of his bombe for production in America.
When Turing arrived in Washington, Joe Eachus of the US Navy’s codebreaking unit showed
him around the city.^7 Turing was fascinated by Washington’s letter–number system of street
names—M Street, K Street, 9th Street, 24th Street, and so on. It was reminiscent of Enigma.
The number streets run north–south and the letter streets east–west, but because twenty-six
letters were not enough, the city planners started the letter names over again at the Capitol,
with C Street SW running parallel to C Street NW but a few blocks further south. Turing’s first
reaction was to ask the key question ‘What do they do in the numbered streets when they get to
26?’ He joked that the numbers should go up as high as 26 × 26—corresponding to a potential
26 distinguished alphabets of 26 letters each—and grinned when he learnt that actually there
are two 1st streets, two 2nd streets, two of everything.
Helping out
Turing had already been involved in US liaison for at least a year by the time he visited
Washington in person. In 1941 he had written out a helpful tutorial for the US Navy codebreak-
ers, whose attempts to crack U-boat Enigma were going nowhere; Turing had politely made
it clear that their methods were utterly impractical.^8 The United States is often portrayed as
responsible for breaking Naval Enigma—for example, in the Hollywood movie U-571 starring
Harvey Keitel and Jon Bon Jovi—but in actuality the truth could hardly be more different.
Another report of Turing’s impressions of the US codebreaking effort survives in the archives,
prosaically titled ‘Visit to National Cash Register Corporation of Dayton, Ohio’.^9 At Dayton,
NCR engineer Joseph Desch was heading up a massive bombe-building programme for the US
Navy. In his report Turing explained that the US bombes would be used as additional muscle,
while the brain work would still be done at Bletchley Park, observing that ‘The principle of
running British made cribs on American Bombes is now taken for granted’.
Turing took the train over to Ohio to advise Desch and electronics expert Robert Mumma,
Desch’s right-hand man on the bombe project. Jack Good, Turing’s Bletchley Park colleague,
described Desch as ‘a near genius’, but Turing still found a lot to criticize in the Dayton bombe
design.^10 ‘I suspect that there is some misunderstanding’, he said sharply at one point in his
report. He also complained:
I find that comparatively little interest is taken in the Enigma over here apart from the produc-
tion of Bombes.
It is not widely appreciated that Turing contributed significantly to the eventual design of the
American bombes. Mumma himself explained the importance of Turing’s visit to the Dayton
project in a 1995 interview.^11 Turing simply ‘told us what we wanted to do and how to do it’,
Mumma said. He emphasized that Turing ‘controlled the design more than anyone else did’.
Secret speech
In January 1943, after a protracted exchange of letters between General Marshall and Sir John
Dill, Bell Labs finally opened its fortress-like metal gates to the shabby British traveller.^12 Turing