The Secrets of Station X (19 page)

The British codebreakers also did everything they could to make the Americans feel at home, Currier recalled.

The Americans were also taken to a number of intercept sites and to London where they were put up in the Savoy and
introduced
to Menzies, Currier said.

Despite subsequent claims that the mission was not as
successful
as the Americans had hoped, the only real threat to
transatlantic
cooperation appears to have come during a visit to the Marconi factory at Chelmsford in Essex. ‘We were stopped at a road block in a small village,’ Currier recalled.

Joe Eachus, a young US naval lieutenant, was sent to Bletchley in early 1942 by Op-20-G, the US naval codebreaking unit, to find out more about the British codebreakers and what they
were doing. ‘My nominal task was to tell Washington what was happening at Bletchley Park,’ he said. ‘In that role I got around to see more of Bletchley Park than a lot of the people who were part of it.’ There was continuing mistrust on both sides. ‘As a liaison officer I was occasionally asked to get specific stuff and on one occasion I was asked by Washington for an
organisational
chart of Bletchley Park,’ Eachus said. ‘I went to the man in charge and said could I have a chart of the organisation. He paused and said, “I don’t believe we have one.” I didn’t pursue this with him, but I was never quite certain whether he meant we don’t have a chart, or we don’t have an organisation.’

Eachus found that the fact that he had his own rations and was happy to share them with the British helped to ease the mistrust. Although there were only two US naval officers, they were officially designated as ‘a detached unit’ and entitled to their own supplies, Joe Eachus recalled. ‘A detached unit covers a multitude of sins, from an individual to a ship,’ he said. ‘So when I went to London I got my supplies from the same place that ships did, sugar in one hundred pound bags and coffee in twenty-five pound cans. So my office was always very well supplied with sugar. Consequently when I would go to some other office to ask them to tell me about what they were doing, I would take a cup of sugar with me, which made me a good deal more welcome than I might otherwise have been.’

Bletchley Park was now playing a critical role in a large number of different military operations around the world. One of the most neglected of these is the codebreakers’ role in what was by any measure one of the most successful intelligence operations in history. The Double Cross System originated with a suggestion at the start of the war by a young MI5 officer, Dick White, that captured German agents should be ‘turned’ to work as double agents for British intelligence. At this stage, the idea was simply to find out from the questions the Germans asked what they did and did not know. One of the earliest
opportunities
to turn a German agent came at the start of the war with the
arrest of Arthur Owens, a former MI6 agent who did a lot of business in Germany and who claimed to have been recruited as the main agent in Britain of the German intelligence service, the
Abwehr
. But when MI5 intercepted his correspondence with his German controller they realised he was playing the two services off against each other. Owens agreed to work as a double agent under the covername of
Snow
. His controller was
Lieutenant-Colonel
Tommy ‘Tar’ Robertson of MI5, who was to become the effective head of the Double Cross system.
Snow
had been given a radio transmitter and a very primitive cypher by the Germans. This was used by MI5 to send false ‘reports’ from
Snow
to his German controller, and was sent to Bletchley Park for
evaluation
. The MI5 radio operator sending the messages noticed that the control station was working to other stations using different cyphers and the messages were sent to Bletchley for analysis. But the codebreaker who looked at them expressed ‘
considerable
disbelief’ that they were of any importance. Despite the codebreaker’s scepticism, the radio messages were monitored by the Radio Security Service (RSS), which employed Post Office intercept operators and a small army of volunteers, most of them radio ‘hams’, who scanned the shortwave frequencies looking for German agent traffic. Major E. W. B. Gill, now head of the RSS, and a colleague, Captain Hugh Trevor-Roper (later Lord Dacre), broke one of the cyphers in use and proved the other messages were indeed
Abwehr
agent traffic. This caused considerable and understandable embarrassment at Bletchley and the row over the significance of the traffic went on for some time with
Trevor-Roper
becoming increasingly unpopular with the professional codebreakers. Eventually, though, Bletchley had to accept that Gill and Trevor-Roper were right and a new section was set up at Bletchley, in Elmer’s School, to decypher the various messages. It was headed by Oliver Strachey and both the section and its
product
became known as ISOS, standing for Illicit Services Oliver Strachey, although the ‘Illicit’ was frequently and
understandably
rendered as ‘Intelligence’. By December 1940, Strachey had
broken the main hand cypher in use on the
Abwehr
networks. The resultant ISOS decrypts enabled MI5 to keep track of the messages of the double agents and spot any other German spies arriving in the UK. It also meant that the agents’ reports could be designed to allow the codebreakers to follow them through the
Abwehr
radio networks. Hopefully, this would help them break the keys for the Enigma cypher that the German
controllers
were using to pass the reports on to Hamburg.

By the end of 1940, Robertson had a dozen double agents under his control. A special committee was set up to decide what information should be fed back to the Germans. It included representatives of MI5, MI6, naval, military, and air intelligence, HQ Home Forces, and the Home Defence Executive, which was in charge of civil defence. The
committee
was called the Double Cross Committee. It met every Wednesday in the MI5 headquarters at 58, St James’s Street, in the heart of London’s clubland. Initially, with the threat of a German invasion dominating the atmosphere in London, it was decided that the ‘intelligence’ provided by the double agents should be used to give an impression of how strong Britain’s defences were. But by the beginning of 1941, it was clear that more could be done with the double agents. They could be used to deceive the Germans, to provide them with misleading information that would give Allied forces an advantage in the field.

Much of the material passed to the Germans was ‘
chicken-feed
’, unimportant information that would give the
Abwehr
a feel that its agents were doing something and had access to real intelligence without telling them anything really harmful. But mixed among this were key pieces of specious or
misleading
information designed to build up a false picture of what the British were doing. While the response of the
Abwehr
controllers to the double agents’ reports helped the Double Cross Committee to work out where the gaps in the Germans’ knowledge lay, it did not tell them whether or not the
misleading 
intelligence picture they were attempting to build up was believed in Berlin. The only way of finding this out was by
decyphering
the messages passed between the
Abwehr
outstations in Paris, Madrid, Lisbon and their headquarters. But these links all used the
Abwehr
Enigma machine, which was completely different to those used by the other German services.

Hut 6 had looked at the
Abwehr
Enigma early in 1941 but had not seen any way to break it so it was handed over to Knox’s research section in the Cottage behind the Mansion at Bletchley. By this stage, the changes to GC&CS introduced to process the main Enigma cyphers had left Knox feeling disconcerted and unhappy. Although Knox’s research section carried out a great deal of vital work that helped the codebreakers of Hut 6 and Hut 8, he felt sidelined and remained angry that the pre-war GC&CS was being turned into a production line by the young mathematicians that Denniston had insisted on bringing in. While the mathematicians were only interested in obtaining the keys to a cypher before moving on to the next problem, Knox was frustrated by his inability to see the decyphering process through to the end. This, combined with the effects of
stomach
cancer, which would eventually prove terminal, made him increasingly irascible. Lever recalled tensions between Knox and Welchman over the way in which the latter had wrested control of the codebreaking operation away from him.

Knox was typically tetchy when Denniston objected, on the grounds of security, to his talking to Strachey about the
Abwehr
radio networks.

‘Dilly spent some time over at the School with his friend Oliver Strachey (the brother of his good Cambridge days friend Lytton) learning about the organisation of the
Abwehr
,’ said Mavis Lever.

Knox sent Denniston a furious note, typically threatening, yet again, to resign, and insisting, rightly, that he needed to see the ISOS material and any other evidence relevant to the
Abwehr
communications, not least for the provision of ‘cribs’, if he were to be able to break the
Abwehr
Enigma. He also insisted that he should be the person reporting any material to London rather than Strachey’s ISOS section of Hut 3, an illustration of how irritated he was by the way in which everything at Bletchley was becoming like an intelligence factory.