104 | 11 BREAkING mACHINES wITH A PENCIl
Dilly. As I soon learned, it was serendipity that counted—although this was serendipity requir-
ing infinitely patient work from Dilly’s assistants. Another difference between the two men
is evident in the relentless seriousness of ‘Prof ’s Book’. Describing Dilly’s rodding methods,
Turing highlighted two kinds of ‘clicks’ (useful repeats in cipher messages) that in his logician’s
way he called ‘direct’ and ‘cross’. In Dilly’s section, we used the more whimsical Knox nomen-
clature of ‘beetle’ in place of ‘direct’ and ‘starfish’ in place of ‘cross’.
Trouble at sea
The need to break German Naval Enigma became ever more urgent, as the U-boats were sink-
ing a horrifying proportion of the merchant shipping crossing the North Atlantic. If only the
Royal Navy could capture the bigram tables used to super-encrypt naval message settings, this
would give Turing a shortcut. (Chapter 10 explains what the bigram tables were.) Admiral
Godfrey plotted cunning schemes with Dilly and Frank Birch, the head of Hut 4 Naval Section.
Dilly suggested obtaining the daily key by asking for it in a bogus signal. A much more ruthless
scheme was put forward by Godfrey’s personal assistant and liaison officer at Bletchley Park,
Ian Fleming, who later wrote the James Bond novels. Fleming devised a plot to crash a captured
German bomber in the English Channel, as close as possible to a suitable German vessel. It was
assumed that the German sailors would hasten to rescue the crew (in their disguise as German
airmen), and once on board the British would heartlessly overpower their German rescuers and
steal whatever Enigma materials could be found.
Turing normally took little interest in the intelligence side of things, but this time he
was anxiously following the plot. However, RAF reconnaissance flights failed to locate any
small and unaccompanied German vessel with Enigma on board, and eventually Fleming’s
‘Operation Ruthless’ was postponed indefinitely. Frank Birch wrote:^13
Turing and Twinn came to me like undertakers cheated of a nice corpse.
Turing and Twinn had to wait until March 1941 when, in a ship-to-ship fight near the Norwegian
Lofoten Islands, the Royal Navy’s destroyer HMS Somali captured crucial Enigma documents
and several Enigma wheels from an armed German trawler Krebs.^14
The recorded date for breaking into German Naval Enigma was the end of March 1941, by
which time Turing and Dilly had parted company. But March 1941 brought a proud moment
for Dilly, too. In the early hours of 29 March, when the last gun was fired in the great sea battle
at Matapan (near Crete), Bletchley Park received this message from Admiral Godfrey:^15
Tell Dilly we have had a great victory in the Mediterranean and it is entirely due to him and his
girls.
Dilly had been put onto Italian Naval Enigma as soon as Mussolini came into the war, in June
1940, and he soon found that the Italians were using the Spanish Civil War ‘K’ model with
additional wheels. The first message to be broken showed that the Italians now had the helpful
habit of spelling out full stops as XALTX, and the full stop at the end of the message was filled
up with XXX to complete the four-letter groups, giving a possible eight-letter crib for rodding.
So it was that a mere full stop contributed so much to the British victory over the Italian fleet at
the Battle of Matapan, described by Churchill as ‘the greatest fight since Trafalgar’.