The Secrets of Station X

by Michael Smith

  ‘The volume of traffic on the one key was enormous,’ Milner-Barry said.

  Over one thousand messages one day, which was broken by five in the morning. I cannot now imagine how, with our primitive methods of collecting and registering traffic, and our tiny staff for decoding it, we manage to cope at all. It is not at all easy now to recapture the atmosphere of those days. The main sensation of the newcomer was that he was participating in a miracle which he was entirely incapable of comprehending. I may say that this sensation has never entirely left me and that no amount of success staled the thrill of the break.

  The long-term significance of the break into the Red using ‘the Herivel Tip’, or Herivelismus as it was dubbed by the other codebreakers, was not entirely clear at the time. But the Red key would never be lost again. It became Bletchley Park’s staple diet. It was used by countless Luftwaffe units and, because they needed to liaise closely with both the Army and the navy in order to provide them with air support, gave an exceptional insight into all the Wehrmacht’s plans for land operations.

  ‘From this point on it was broken daily, usually on the day in question and early in the day,’ recalled Peter Calvocoressi, one of the members of Hut 3. ‘Later in the war, I remember that we in Hut 3 used to get a bit tetchy if Hut 6 had not broken Red by breakfast time.’

  There was very little that the Bletchley Park material could do at this stage to influence the Battle for France, but efforts were made to develop the process previously used in Norway of passing the Enigma decrypts, now known by the codeword Ultra, to British commanders in France. This was done by an MI6 communications link to the headquarters of the British Expeditionary Force. A copy of the Hut 3 ‘agent report’ was passed to the MI6 Codes Section, which was based in Bletchley Park and which encyphered it using one-time pads, which when used properly are unbreakable. The encyphered report was then sent by motorcycle dispatch rider to the wartime headquarters of Section VIII of MI6, which was based at nearby Whaddon Hall, and from there it was sent on the MI6 radio link to the MI6 representative at GHQ in France. The codebreakers were jubilant when they decyphered a message giving eight hours’ notice of a meeting between the chiefs of staff and the four Luftwaffe formations involved but their joy turned to disappointment when the British commanders ignored the intelligence and the opportunity to bomb the meeting and kill key German commanders.

  ‘Valuable as this mass of Special Intelligence might become after analysis as the foundation of strategic knowledge of such matters as the enemy’s order of battle, it was clearly of little if any immediate tactical use,’ Birch recalled.

  Hut 3 had not as yet the experience, the collateral information or even the reference books and maps wherewith to disentangle the obscurities of the German texts; few in the ministries could currently assess their significance in their disguised form, recipients in the operational theatre could only take them at their face value as agents’ reports; not many of them arrived in time for action to be taken; and even if all the material had been available and correctly appreciated, it is doubtful whether in the prevailing confusion, any practical use could have been made of it. Disguised and mutilated to resemble an agent’s report, it lost its integrity, did not inspire confidence and could not be correctly assessed.

  But in real terms the dismissive attitude of the military at this time to any intelligence produced by Bletchley Park was irrelevant during the Battle for France, which was already lost by the time Red was broken. The Allied troops were already in full retreat and even if they had accepted that the intelligence was accurate, they would have been in no position to make proper use of it. Nevertheless, vital lessons were learned allowing the system to be revised so that Ultra intelligence could have a direct effect on any future campaigns fought by British troops. It was clear to Menzies and the directors of intelligence in the Admiralty, War Office and Air Ministry that they had to find a way to get the Bletchley Park intelligence, now distinguishable by the classification Most Secret Ultra which appeared at the top and bottom of each sheet of the reports, to commanders in the field, with someone involved in the reporting process on the ground fully aware of where the information came from and its true value while at the same time protecting it and limiting knowledge of the fact that the British codebreakers were reading the Enigma messages.

  The issue was discussed at cabinet level and in mid-June 1940, the War Office set up a mobile Special Signal Unit, the role of which was to provide liaison with major commands so that Ultra intelligence from Hut 3 could be passed on direct. The unit was in fact run by Richard Gambier-Parry, head of Section VIII of MI6, and its original title of Special Signal Unit did not last long because the abbreviation SSU was assumed to be Secret Service Unit. The units were later split into two with Secret Communications Units attached to all major command posts to provide the communications links via which the Ultra intelligence would be passed and Special Liaison Units set up and controlled by Frederick Winterbotham, the head of the MI6 Air Section, alongside them passing the intelligence on to commanders.

  Although it would be a year before the SCUs and SLUs would play their real role, they were to be critical to the future use of Ultra intelligence by operational commanders. They were designed to provide the intelligence produced by the codebreakers swiftly and securely to commanders in the field. The SCUs were the communications experts linking the unit to the codebreaking centres, while the SLUs were made up of intelligence officers provided by MI6, who passed the Ultra material on to the commanders. Their role was to control the use of all high-grade signals intelligence, not just Enigma material, strictly to ensure that only those who had been indoctrinated knew of its existence. They also had to enforce the regulations on its use, making sure that it was never acted upon without a secondary source being available, to prevent any German suspicion that Enigma had been broken, and to liaise with the codebreakers on any queries from commanders.

  The SLU officer was responsible for personally delivering the Ultra message to the commander or to a member of his staff designated to receive it. All messages were to be recovered by the SLU officer as soon as they were read and understood. They were then destroyed. No Ultra recipient was allowed to transmit or repeat an Ultra signal. Any action taken by a commander on the information given him by Ultra was to be by way of an operation order or command or instruction which in no way referred to the Ultra signal and could not lead the enemy to believe his signals were being read. No recipient of Ultra could voluntarily place himself in a position where he could be captured by the enemy.

  The procedures used within Hut 3 were also altered in the light of lessons learned during the Battle of France. The amount of material coming in had strained its resources to the limit. Hut 3 itself became more organised and the number of staff increased with four reporters on each watch and with one officer from each of the Air and Military Sections of MI6 sat on each watch as Air or Army advisers, significantly upgrading the basic two-man watches that were clearly not sufficient during the fighting in Norway and France. ‘Hut 3 and Hut 6 were side by side,’ said Ralph Bennett, one of the watch intelligence reporters. ‘They were linked by a small square wooden tunnel through which a pile of currently available decodes were pushed, as I remember by a broom handle, in a cardboard box, so primitive were things in those days.’

  The messages arrived through the wooden tunnel from Hut 6 in batches of between fifteen and twenty and were immediately sorted into different degrees of urgency by the Watch No. 2, or Sorter. They were split into four separate piles. Pile 1, by which the Hut 3 priorities would remain known throughout the war, was the most urgent messages. Pile 2 was less urgent but still needed to be processed and turned into agent reports within four to eight hours and Pile 3 needed to be reported but could be safely sent to MI6 headquarters at Broadway Buildings in London by overnight bag. The fourth pile was nicknamed the Quatsch pile after the German word for rubbish and did not need to be processed at all, although they were kept on file for
future research.

  ‘Skimming the incoming material to assess urgency and importance remained the most responsible and tricky job,’ recalled Lucas.

  It would have been sufficiently troublesome, even if all decodes had arrived in an easily readable state (as a small proportion did throughout), since the pure intelligence problems involved were often extremely difficult to solve on the spur of the moment – a difficulty which became even worse later on, as our work grew more complicated. But since a high proportion of decodes were corrupt, sometimes very corrupt, it was often impossible, on a necessarily cursory reading, to assess the importance, or even the simple sense, of a message. Thus, in times when there was much material (and in Hut 3 we usually had too much to do or else, though rarely, too little) the Sorter had a heavy responsibility, since by a simple mistake he could cause an obscure but urgent message to be laid aside for hours or even days.

  Hut 3 was set up like a miniature factory with the Watch Room at its centre. The Watch sat around a circular or horseshoe-shaped table, with the Watch No. 1 at the head of the table, while the air and military advisers sat at a rectangular table to one side. There were up to half-a-dozen men on the Watch, each of whom had to deal with a message taken from the highest priority pile in which there were messages, first of all ‘emending’ them, i.e. filling in any gaps left because of radio interference or garbled letters, a process that had similarities to solving a crossword puzzle. They then compiled an alleged agent’s report based on the message, working from the original German, rather than translating it first, in order to guard against the introduction of errors.

  ‘The watchkeepers were a mixture of civilians and serving officers, Army and RAF,’ said William Millward, an RAF officer who worked in Hut 3 as an air adviser.

  I cannot remember any women involved in this part of the operation, presumably because it was still thought to be wrong for a woman to work on the night shift or because it was thought to be a man’s job. At the rectangular table sat serving officers, Army and RAF, one or two of each. These were the Advisers. Behind the head of Watch was a door communicating with a small room where the Duty Officer sat. Elsewhere in the Hut were one large room housing the Index and a number of small rooms for the various supporting parties, the back rooms.

  Once the watchkeeper had written the report it was checked by the Watch No. 1, who then passed it to either a military or an air adviser depending on the content. The adviser’s job was to ensure it made military sense and to add any comments on what was previously known about the unit before passing it back to the Watch No. 1 so that it could be teleprinted to London.

  ‘Material came in from Hut 6 in more-or-less cablese German and a lot of it corrupt,’ said Jim Rose, another of the air advisers.

  Urgent messages were sent direct to Commanders-in-Chief. All messages went up to the service ministries. If the air adviser or the military adviser had anything to comment he was allowed to do so and then next morning we would send deeper comment to the Commander-in-Chief. Some of the information was tactically immediate, some of it was strategic and some of it was a build-up of order-of-battle, strength, weaknesses, supplies and so on, which most generals don’t know about their enemy. So it was very important in so many ways.

  Meanwhile, Nigel de Grey was put in charge of an ‘Intelligence Exchange’ Section, Hut 3a, to work on long-term intelligence analysis and reporting. ‘There was an inevitable tendency for us to concentrate on the more urgent and spectacular aspects of our information,’ Lucas said, ‘to try to send out intentions and front lines, battle HQs and tactics with all possible speed, while ignoring by comparison matters of more lasting interest such as organisation, strength, habits of the Luftwaffe and the German Army and so on.’ De Grey’s role was to remedy that by setting up a group of backroom analysts and reporters. One of their first tasks was to set about acquiring more detailed maps than the Baedeker tourist guides the Hut 3 Watchkeepers had been forced to work with during the campaigns in Norway and France. They also looked at the various terms used by the Germans, many of which had completely baffled academics more used to translating Goethe than Guderian; and, most importantly of all, began to build up a detailed picture of the structure of the German armed forces.

  The fall of France cast a dark shadow over everyone at Bletchley Park, but the French liaison officers from ‘Mission Richard’ were clearly worst affected. ‘I remember seeing several of the Frenchmen who were attached to the French Mission here clustered around the wireless set with their ears almost glued to it,’ said Phoebe Senyard. ‘They were listening to very faint announcements made by the BBC, or getting on to a French station and becoming more and more dejected and downcast with every fresh announcement.’

  Mavis Lever was eating her dinner in the mansion dining hall when the news that Paris had fallen was announced. ‘We had some Frenchmen working with us at the time and I was sitting next to one of them and he burst into tears,’ she said. ‘I simply did not know what to do. So, I went on eating my sausages. I mean we weren’t going to get any more and it seemed to me there was nothing really I could do if other people were going to burst into tears. I’d got a night shift to work on, so on with the sausages.’

  Following the German invasion, Bertrand and the Poles set up a new station on a country estate, the Château de Fouzes at Uzès in Provence, working with the Vichy French government’s Groupement des Controles Radioélectriques. This was supposed to be monitoring British communications with the underground resistance movement but in fact assisted Bertrand and the Poles by intercepting Enigma traffic and allowing them to continue to do their work on Enigma. Bertrand also managed to make contact with Bletchley Park, via MI6. They remained there until the Germans occupied the whole of France in October 1942 when they escaped to the UK.

  Hut 6 was at this stage still breaking Enigma keys by hand using the Cillies and Herivelismus and waiting for Turing’s Bombes to help them. The first of the Bombes, known with misplaced optimism as Victory, had been produced in the space of three months and had come on stream in March 1940. It was a fast running electrical machine in a bronze cabinet six-and-a-half feet high, more than seven feet wide and two-and-a-half feet deep, containing a series of thirty rotating drums equating to the wheels of ten Enigma machines, although later versions simulated the action of twelve machines. It contained around ten miles of wire and about a million soldered connections.

  The Bombe was a remarkable piece of technology for its time. It was designed to run through all the various possibilities – of wheel choice, order, ring position and machine settings – at high speed in order to test that the Cillies or cribs suspected by the codebreakers were actually in use. The codebreakers provided the operators with a ‘menu’ suggesting possible equations of clear letters to encyphered letters which was fed into the Bombe. Each time the machine found a possible match, it stopped and was quickly tested by the operator on a British Type-X cypher machine rigged up to work like an Enigma machine to see if it produced German text.

  If it did, the operator was able to declare: ‘The job’s up’ and pass it back for decryption. If it was just garbled letters, as was frequently the case, the process continued until the Bombe had found the right combination or exhausted all the possibilities, in which case the codebreakers’ suspected crib or Cilli didn’t work and a new one had to be found. But Victory kept making ‘false stops’ and took far too long to test a single ‘menu’ so it was only used on Naval Enigma, which was not yet being broken on a regular basis. Welchman suggested a solution of a diagonal board to cure the ‘false stops’ and Turing immediately agreed this would correct the problem. It was not until August 1940 that the first of the Bombes with the diagonal board, Agnus Dei, later corrupted to Agnes or even Aggie, was introduced, assisting Hut 6 in its breaks into the Enigma cyphers.

  With the end to fighting in France and Norway, the Germans turned their attention towards Britain. Concerns over the possibility of an imminent invasion pervaded the atmosp
here at Bletchley Park. ‘The sinister covername for an Operation Sea Lion began to appear in the Luftwaffe traffic,’ said de Grey. ‘It did not require much ingenuity to identify this name with the preparations for invasion which continued unabated throughout the late summer and early autumn.’

  Neville Chamberlain’s association with appeasement and the inadequate response to the German attack on Norway had led, at the beginning of May, to his resignation and replacement by Winston Churchill, the man who had ordered Room 40 to be set up. The new Prime Minister soon became obsessed with Bletchley Park, treasuring the intercepts delivered to him each day by Stewart Menzies, the Chief of MI6 and Director of Bletchley Park, in a battered old wooden dispatch box covered in fading yellow leather.

  With Hitler’s next move expected to be an attack on Britain itself, Churchill made a series of speeches aimed at building up ‘the bulldog spirit’. They were epitomised by his ‘finest hour’ address to the House of Commons and his warning that the British would defend their island on the beaches. Detachments of Home Guards were set up around the country and Bletchley was no exception. Some of the codebreakers were enthusiastic recruits. Malcolm Kennedy recorded in his diary that there had been a wireless appeal ‘for volunteers between seventeen and sixty-five to form local defence units against parachutists. I sent in my name to join the detachment which is to be formed at Bletchley, so I may yet have a chance to take a smack at Brother Boche once more!’

  One of the more surprising members of the Bletchley Home Guard was Alan Turing. But in typically eccentric fashion he did it solely on his own terms, joining only in order to learn how to fire a rifle, said Peter Twinn. ‘They told him to fill this form in and Turing thought to himself: “I don’t see why I should sign this, it won’t do me any good and it might be a bit inconvenient.” So when he’d learned how to fire a rifle and done as much as he thought was of value to him, he thought: “Well, I’ve got everything I can out of this, I’ll just give up going to the Home Guard.” When the officer in charge said he would do what he was told because he had agreed to be subject to military discipline, Turing replied, and I can hear him saying it: “Well, you had better look at my form. You’ll see I didn’t sign that bit”.’