The Secrets of Station X

by Michael Smith

  Ann Harding, a colleague of both ‘Prof’ Turing and Peter Twinn in the German Naval Section Hut 4, recalled that the men taking part in the Home Guard were known as ‘parashots’ since they were expected to shoot the German paratroopers as they tried to land. ‘Most of the men had become parashots,’ Harding recalled. ‘One day Prof had an awful thought. “Peter, what do we do if they land in the maze? There would be the most awful muddle, Peter, with us and them getting lost.” This was quite a thought as it was a large maze. The threat of invasion was very real. Many people had heavy sticks or, in the case of farms, pitchforks hidden behind their doors, ready to attack.’

  Noel Currer-Briggs, an Intelligence Corps officer, recalled that at one point a mixture of the Home Guard and the regular Army marched into Bletchley as part of an Army recruiting campaign. ‘There were lots of oddballs there, people from all over Europe with obscure languages, and there was one chap from Eastern Europe in battledress and a bowler hat, much to the dismay of the sergeant who was trying to make us look smart. It made Dad’s Army look like the Coldstream Guards.’

  Plans were put in place to set up a mobile codebreaking unit to operate behind the defending British troops should the Germans manage to cross the Channel. The codebreakers’ records were to be evacuated to Canada and there was even talk of moving GC&CS across the Atlantic as well if need be.

  ‘The war situation was now becoming very grim,’ said Phoebe Senyard.

  So during the ghastly months of May, June, July and August when the fear of German invasion was greatest, arrangements were made to organise a mobile section of GC&CS. The air was electric with feeling. Those who had been chosen were photographed and supplied with special passports or identification cards and were in a sense excited by the project, although no doubt dismayed by the reason for their evacuation. I was surprised at the number of people whose feelings were hurt because they had not been included in the list, while certain of the more lighthearted and venturesome of the section came out with suggestions of what we could do should the Germans come and how we could advance our careers under the German Herrenvolk. Joking apart, times were very serious and air raid alarms were continuous night and day. We used to use the slit trench at the back of Hut 4 until it was declared unsafe. Special orders were issued about the dispersal of staff should Bletchley Park be attacked and so the gloomy days wore on.

  Column BQ, as the mobile unit was to be called, was to comprise around 500 people: 140 of the codebreakers and 360 wireless operators from the various Y stations. The transport was to be a mixture of private cars and four ancient Midland Red buses, hired by the War Office, one of which promptly split along the length of its roof while the other three continuously broke down. ‘I am told that the petrol consumption is about five miles to the gallon,’ complained one of the column’s organisers, ‘and I think it questionable if they had to go a long journey whether they would arrive at their destination with any degree of certainty.’

  Most of the private vehicles were in somewhat better condition, although possibly no less dangerous. One of the cars volunteered as Column BQ transport was the grey Bentley driven by Diana Russell Clarke, who had become renowned for driving it at breakneck speed along the country roads around Bletchley. ‘There was one occasion when I was coming back from leave going about sixty-five which now we would think was very slow, and burst a front tyre,’ she said.

  The car went into a frightful wobble. But eventually I got it onto a nice wide verge. There was a car coming from the other direction and the occupant got out to see if I was alright. It turned out to be Commander Travis. He said: ‘My God, I might have realised it would be you, Diana.’ I’d obviously frightened him to death; he thought I was going to go straight into him.

  Fortunately, the invasion never came and neither the Bentley nor the buses were ever needed. The codebreakers were able to remain at Bletchley Park where it was not simply a question of breaking Enigma. Hitler and his generals realised that if they were to invade Britain they would need to control the skies otherwise the RAF and the Royal Navy would cause major, probably critical, damage to their forces as they tried to land. So on 10 July 1940, the Luftwaffe launched a series of attacks on coastal ports, and subsequently on RAF airfields and aircraft factories, that was to become known as the Battle of Britain. The name of the battle came from a speech made by Churchill in the House of Commons on 18 June in which he said that the Battle of France was over and the ‘Battle of Britain’ was about to begin.

  Upon this battle depends the survival of Christian civilisation. Upon it depends our own British life, and the long continuity of our institutions and our Empire… Let us therefore brace ourselves to our duty, and so bear ourselves that if the British Empire and its Commonwealth last for a thousand years, men will still say, ‘This was their finest hour.’

  The role of Bletchley Park and signals intelligence in tracking the German bombers and fighters attacking the UK is not widely known but the Air Section, which had a dual role as a GC&CS section and as a section of Air Intelligence, AI4f, was able to break the low-level codes used by the Luftwaffe to control the German bombers flying from their airfields in France to attack the UK. ‘Exploitation of this material for intelligence purposes should have been a moderately straightforward process,’ said Bill Bonsall, a member of the Air Section who would later go on to become the head of its post-war successor GCHQ.

  No great brainpower and no special machinery were needed. It was essentially a pencil and paper operation. But in practice unnecessary obstacles had to be overcome before it reached its full potential, the main one being the Air Ministry’s view that the role of GC&CS should be confined to codebreaking. It maintained this view for the first half of the war.

  Bonsall was recruited to Bletchley by Martin Charlesworth, one of the dons who had been inculcated in the work of GC&CS at the start of the war but had stayed as President of St John’s College, Cambridge, to talent-spot potential codebreakers. He and another candidate were invited to Charlesworth’s rooms where Denniston and Tiltman were waiting to interview him. ‘They asked us if we were interested in confidential war work,’ Bonsall recalled.

  We both said yes and were told that we would be hearing further from them. After a delay of some weeks, I received a letter instructing me to Bletchley Junction, telling nobody, not even my parents, where I was going. I was duly met and taken to the Mansion, where I signed a copy of the Official Secrets Act and was given the address of a billet in the Buckingham Road. When I reported back the following morning, I was taken round to Hut 4 and introduced to Joshua Cooper who said I was going to be working on the radio communications of the German Air Force. Within minutes, I was seated at a trestle table copying out coded messages onto large sheets of paper.

  Given the RAF’s approach to the codebreakers, which was epitomised by Blandy’s initial insistence that Cheadle should not get involved in producing ‘stuff for people at Bletchley to fool about with’, the refusal to allow the Bletchley Park Air Section to send out intelligence reports was perhaps less of a surprise than it should have been, but Josh Cooper found a way round the problem. He attached his own people to each of the wireless intercept shifts at Cheadle to break the basic Luftwaffe codes alongside the operators with Air Intelligence, agreeing that they could provide intelligence rather than the raw signals. These would have otherwise been largely unintelligible to their recipients, who included RAF Fighter Command at Bentley Priory north of London, from where the fighter defences were controlled. ‘I applied to the Air Ministry for a number of Computor Clerks,’ Cooper said. ‘This curious title had nothing to do with electronic computers, which had not yet been invented, but was an echo of an old War Office covername for cryptanalysts – Signal Computor. A successful Computor Clerk watchkeeper was going to need considerable initiative, and would have to fit in with the special world of Cheadle radio operators.’ The ‘Computors’, as they were known, were trained up at Bletchley before being sent to Cheadle and the mo
ve proved highly successful, said Bonsall.

  Arriving shortly before the Germans invaded Western Europe the ‘Computors’ soon achieved their primary task of breaking the air/ground codes completely and quickly enough to derive current intelligence from them. The original three-letter codes were replaced in 1941 by three-figure codes. These codes were harder to break but the ‘Computors’ developed techniques which resulted in their being broken quickly and completely enough to yield intelligence. To begin with, the ‘Computors’ worked in the main set-room, with the result that their raw material reached them quickly and the operators could see that their intercepts were eagerly awaited.

  The Luftwaffe low-level communications between the aircraft and ground controllers were intercepted by Cheadle and, increasingly as the Luftwaffe communications switched to VHF, by a network of small RAF mobile and fixed Home Defence Units based along the eastern and southern coasts at Peterhead and Fifeness in Scotland, Blyth in Northumberland, Scarborough, Skegness, Gorleston, Harwich, Fairness, South Foreland, Hawkinge, Beachy Head, Portsdown Hill, Portland Bill, Strete (near Dartmouth), Coverack and Hartland Point. This network, which was coordinated by RAF West Kingsdown in Kent, provided vital tactical intelligence on the preparations of the German bombers and their fighter escorts. Bletchley gave advance notice of the planned times of raids, the intended targets and the numbers of aircraft involved.

  The introduction of the ‘Computor Clerks’ to Cheadle had allowed Cooper to find a way around the RAF chiefs’ perverse view that one of their own intelligence branches should not be allowed to produce intelligence. Under his direction, the Bletchley Air Section had complete mastery of all the Luftwaffe low-grade codes and cyphers. ‘Its cryptanalytic achievement was formidable,’ said Birch. ‘With far more lower grade German material to deal with than the other Service sections, it could claim at the end of 1940 that all known Luftwaffe non-machine cyphers were readable; of meteorological cyphers, four German, five Russian and two Italian had been read.’ Cooper was an extraordinarily astute man whose career in signals intelligence, or Sigint as it is known in the jargon of the codebreaker, went on to span the inter-war period, the Second World War and the Cold War, but he became known to many who arrived at Bletchley during the war as one of the more unusual of the senior staff.

  Ann Lavell, who arrived at Bletchley in July 1940 as an 18-year-old WAAF, became Cooper’s PA. She recalled that he had a distinctively nervous habit of putting his right hand behind the back of his head and stroking his left shoulder. She found his eccentricity difficult to deal with. ‘He was absolutely mad, frightening really,’ she said.

  At first I didn’t like him at all. I thought he was horrible. But when I got to know him I got quite fond of him. But he was not really one of us. He was on another plane, I think. He’d get awfully embarrassed and worried when he felt he wasn’t acting like an ordinary human being. There was one time when he kicked over a fire extinguisher and it started foaming and he didn’t know what to do and he picked it up, rushed to and fro, and a friend of mine went and took it from him and put it out of the window. He wasn’t very practical but once you knew him and got over the slightly forbidding exterior he was very nice and very kind. I’ve got a rather delightful caricature of him, doing this very familiar gesture of right hand behind head and scratching left ear.

  Once they were standing beside the lake and Cooper was drinking a cup of coffee. When he finished he stood there with the empty cup and was clearly slightly embarrassed by having it in his hand. ‘So he just threw it in the lake,’ Lavell said.

  R. V. Jones recalled that Cooper was frequently asked to take part in interrogations of pilots. The first time he did this, he and two other interrogators were sat behind a trestle table when the captured Luftwaffe pilot, wearing perfectly pressed Nazi uniform and highly polished jackboots, was marched in and halted in front of them. ‘He clicked his heels together and gave a very smart Nazi salute,’ said Jones.

  The panel was unprepared for this, none more so than Josh who stood up as smartly, gave the Nazi salute and repeated the prisoner’s ‘Heil Hitler’. Then realising that he had done the wrong thing, he looked in embarassment at his colleagues and sat down with such a speed that he missed his chair and disappeared completely under the table.

  Gwen Davies, another member of the Air Section, remembered Cooper as being ‘a very, very strange man, who would burst into the watch sometimes and shriek something absolutely unintelligible and burst out again’. Most of the junior members of staff had difficulty understanding what he was saying, but there was no doubting his brilliance.

  There was a great degree of tolerance at Bletchley for eccentricities. There had to be because so many of the people were very, very eccentric indeed. At least half of the people there were absolutely mad. They were geniuses, no doubt many of them were extremely, extremely clever, but my goodness they were strange in ordinary life.

  As the number of messages on the Red cypher dropped due to the decline in German offensive operations, Hut 6 had much less work but on 2 September 1940, a new Enigma key, Brown, was broken with the aid of Cillies and the newly introduced Bombe Agnus Dei. The messages in the Brown Enigma had risen during the late summer of 1940, when the Battle of Britain was in full swing and the RAF Hurricanes and Spitfires were fighting off the Luftwaffe daytime bombing raids, said Stuart Milner-Barry. ‘Nobody knew what its contents would be and the most extravagant hypotheses were entertained.’ The Brown traffic was found to be communications between a number of Luftwaffe stations in France which were directing wireless beams across Britain to guide the German bombers to their targets. It was a critical moment and the timing of the break could not have been more opportune. Having lost the Battle of Britain, the Luftwaffe was about to switch to the period of night-time bombing that would become known as the Blitz. The breaking of the Brown Enigma was to give Bletchley the first of a number of major contributions to the war effort.

  ‘It proved a delightful and a most entertaining key cryptographically,’ said Milner-Barry,

  because although the traffic was small, the density of cribs and of Cillies was phenomenal. Never before or since have so many and such gross breaches of the most elementary rules of cypher and procedural security been committed as by the specialists in beam bombing. They never learned and the German signals officers apparently were powerless to intervene. It was also extremely exciting because of course the object of the exercise was to discover the target before it was too late to be of use to the Air Ministry. The handling of Brown, moreover, gave us our first insight into the necessity of close liaison between intelligence and cryptography.

  After the famous ‘Few’ had swept the skies of Britain clear by day, Hut 6 played its part in rendering the skies as hazardous by night. As most raids took place in the early evening, just after dark, the time factor was constantly on the thoughts of the cryptographer and a sense of urgency, such as was never felt again, permeated the whole Hut. For, never again, was the battle so close that the results of one’s work had an immediate personal interest, when the difference of an hour in breaking time might mean the difference between life and death for some inhabitants of this embattled island.

  R. V. Jones was already convinced that there was a system of German wireless beams criss-crossing the UK to guide the Luftwaffe bombers onto their targets. These had been mentioned by captured German prisoners-of-war and a piece of paper salvaged from a Heinkel bomber shot down in March 1940 referred to ‘Funkfeuer Knickebein’, or in English ‘Radio Beacon Dog-Leg’. The word Knickebein recurred on a low-level coded message intercepted by Cheadle. Jones recalled getting a call from Professor Frederick ‘Bimbo’ Norman, the pre-war Professor of German at King’s College, London, and one of the Hut 3 reporters, in the early hours of the morning one day at the beginning of September 1940.

  ‘Two or three nights before the bombing of London started on 7 September, my sleep was interrupted by an event which made more impression on my memory than an
y bomb ever did,’ Jones said.

  The cryptographers had broken a new line of Enigma traffic. There was mention of beams, including one which said that the beam width was eight to ten seconds of arc, or an angle of one in twenty thousand, which would imply that the beam was no wider than twenty yards at two hundred miles. I asked Bletchley to put every possible effort into making further breaks into the new line of traffic. If only we could decode the Enigma messages in time, we could find where and when the German bombers were going to attack and so counter them by having fighters waiting and by having our jamming ready on the right frequencies. This would make great demands on the codebreakers, for the orders did not go out to the beam stations until the afternoon, giving only two or three hours to make the break, but for such a prize they strained every resource of human intelligence and endurance; and it was a great day, late in October, when they achieved this fantastic feat for the first time.

  Despite the codebreakers’ frequent ability to break the Brown, providing ‘vital intelligence’ that allowed the RAF fighters to lie in wait for the German bombers, it was occasionally impossible. This was sadly the case with one of the most devastating bombing raids carried out by the Germans, against Coventry on 14 November 1940. Enigma had revealed that there was to be a major operation against the UK on that day and that it was codenamed Moonlight Sonata, but the only clue to what it might be was the vague mention of a codeword Korn (the German for corn). There was no indication as to what it meant but it later transpired that it was an alliterative code for Coventry which the Germans spelt with a K. On the day itself, the Brown Enigma could not be decyphered. The raid on Coventry destroyed 4,000 homes, three-quarters of the city’s industry and killed as many as 600 people, injuring more than a thousand others. After the secret of the breaking of the Enigma cyphers emerged in the 1970s, a myth grew up that Churchill had insisted that the RAF should not attempt to stop the raid going ahead in order to prevent the Germans realising that Enigma had been broken. It was certainly the case that there was concern that the way in which the RAF fighters were waiting for the Germans and the air raid precautions put in place in the target areas might lead the Germans to suspect that Enigma was being broken but this played no role in the Coventry raids and the initial concerns over the effect on Enigma were not at any event raised until some time after the Coventry raid.