102 | 11 BREAkING mACHINES wITH A PENCIl
that there was little that he, Rejewski, could tell him. ‘Knox grasped everything very quickly,
almost as quick as lightning’, he said.^4
As soon as Dilly returned from Warsaw, he sent the three Polish mathematicians a note,
thanking them sincerely for their ‘co-operation and patience’, together with three silk scarves,
each showing a horse winning the Derby, a very gracious acknowledgment. He also sent a set of
‘rods’, his small lettered strips of cardboard that reproduced the action of the Enigma’s wheels.
These rods were the basis of Dilly’s own method, and he had been almost in sight of the winning
post himself. As soon as Dilly gave Rejewski’s missing piece of information about ABCDE . . .
to Peter Twinn, Twinn unmasked two of the Enigma machine’s wheels in only two hours, using
the monster crib and Dilly’s rod method.
Difficult to anchor down
Dilly invited Turing to join him at his home, Courns Wood, so that he could tell him all about
the Warsaw conference. Closeted in his study, he held an inquest on his failure to achieve what
Rejewski had done. After Turing left Courns Wood, Dilly wrote his official report on the Pyry
conference, dated 4 August 1939, and marked ‘Most Secret’.^5 In it he reported that Rejewski had
indicated to him that the Polish solution was achieved by mathematics. Dilly was anxious to
know whether this was true, and whether it was his lack of mathematics that had held things up.
His report said that Turing had helped to convince him that this was not so.
Gordon Welchman, a first-class Cambridge mathematician, joined the Cottage party at the
same time as Turing. He soon shone, and became the head of Hut 6 in January 1940. Welchman
was a prime mover in turning Dilly’s cottage industry into a factory production line—rather to
Dilly’s horror. According to Welchman, Dilly was ‘neither an organisation man nor a technical
man’ but ‘was essentially an idea-struck man’.^6 Turing was not an organization man either, but
he was a technical man, and (like Knox) was a fountain of brilliant ideas. A ‘Most Confidential’
memo that Dilly wrote about his newly arrived staff gives a glimpse of how he saw Turing:^7
Turing is very difficult to anchor down. He is very clever but quite irresponsible and throws out
suggestions of all sorts of merit. I have just, but only just, authority and ability to keep his ideas in
some sort of order and discipline. But he is very nice about it all.
Much to Dilly’s disappointment, the French government would not allow the Poles to leave
the Château de Vignolles, the country house near Paris where a joint Polish–French cipher
bureau had been set up following the Poles’ escape from the advancing German forces. While
still in Poland, the Polish codebreakers had invented what were called ‘Zygalski sheets’—
perforated cardboard sheets showing repeated positions of letters in the doubly enciphered
indicators—but they never had the resources to manufacture enough of these. Turing couriered
the last package of a consignment of British-made Zygalski sheets to Château de Vignolles,
and found the Poles anxious to know more from him about Knox’s methods. They probably
did not already know about what Dilly called ‘cillies’, where a slack operator used the finishing
position of the wheels for the start of the second part of a two-part message. Cillies helped to
reduce quite dramatically the number of Enigma settings that the codebreakers had to test.
Rejewski admitted that there was also ‘another clue for which we had the British to thank’.^8 This
was Dilly’s ingenious discovery that a seemingly unimportant weather code in fact gave away
the Enigma’s plug connections for the day, because the Germans were foolishly using the letter