by R. V. Jones
At the meeting with Tizard an interesting sidelight emerged. Nutting had with him one of his Deputy Directors, Group Captain Lang, who told us that the latest Chiefs of Staff appreciation of the war situation was that invasion was possible within a week, likely within two weeks and almost certain within three. I did not myself believe it, but it gives some idea of the atmosphere in which we had to operate.
I could see that despite the priority we already had, progress might be held up because of insufficient scientific manpower. I therefore persuaded Lindemann to minute Churchill for authority to devote to the task anyone whose research was not likely to affect production in the next three months. Winston initialled the minute with the comment ‘Let this be done without fail’. Curiously, Hitler had given a very similar order regarding German research at about the same time, for the opposite reason that he regarded the war as nearly won.
In the afternoon of the same day I attended a meeting in Watson-Watt’s office, to decide the ways in which we could fulfil the decisions of Joubert’s meeting. We selected five of the radar stations in the main coastal chain as sites at which we would try to detect the beams from the ground. Ottercops, Staxton Wold, West Beckham, Bawdsey, and Dover. We also selected the R.A.F. Unit that would try to detect the beams in the air. This was the Blind Approach Development Unit stationed at Boscombe Down, whose pilots had more experience than any others in flying along Lorenz-type beams. Their Commanding Officer was Wing Commander R. S. (Bobbie) Blucke, with whom I had flown several times when he commanded the Experimental Flight at Farnborough, and who had piloted the Heyford bomber used as target in the very first radar trial in February 1935.
It may help here if I explain what a Lorenz beam is, for this is what we expected to find. If one arranges a number of aerial units (‘dipoles’, which look like the simplest type of television aerial) side by side, as in a fence and about the same distance apart as they are long, and feeds the radio energy to them in a suitable manner they will generate the beam which emerges broadside to the fence; and, paradoxically, perhaps, the longer the ‘fence’ the sharper the beam. But without a fence of prohibitive length, the beam would not be nearly sharp enough to define a target one mile wide at two hundred miles range. The clever trick in the Lorenz system was to transmit two fairly blunt beams, pointing in slightly different directions but overlapping one another in a relatively narrow region which now in effect becomes the ‘beam’ along which the aircraft are intended to fly. (Figure 1)
Fig. 1. Principle of the Lorenz beam
The two overlapping beams are most simply generated by two aerial systems pointing in slightly different directions and mounted together on a single turntable. The actual radio transmitter is switched from one of these aerials to the other and back again in a repetitive sequence, so that one aerial transmits for a short time followed by a longer interval, giving a ‘dot’ to anyone who listens to it on a suitable radio receiver, while the other transmits for a long time followed by a short interval, giving a ‘dash’. Anyone so placed as to receive the two aerials at the same strength would hear the one transmit a dot immediately followed by the other transmitting a dash, so that he would think that he was listening to a single aerial transmitting continuously. As he moved sideways into the zone in which one beam, say the ‘dot’ beam, was stronger than the other, he would begin to hear the dots coming up above the continuous note, and vice versa with the dashes. By listening for the predominance of dots or dashes he would know the direction in which he would have to steer to bring himself back into the narrow ‘equisignal’ zone. This zone can be as narrow as one hundredth or even one thousandth of the width of the ‘dot’ or ‘dash’ beam alone. The aerials are therefore set on the turntable in such a direction that the equi-signal zone passes over the target. To warn the pilot that he is approaching the target, a similar beam system would be set up from one site well to the side of the director beam, and this second system would transmit a marker beam to cross the director a few kilometres before the target.
So this was what we had to look for. The radio frequency had to be within range of the ‘hotted-up’ Lorenz-type receiver in the Heinkel III which put it between 28 and 35 megacycles per second, and Rowley Scott-Farnie said that it would very likely be exactly 30 or 31·5 or 33·3 because these were pre-set frequencies in the German receivers. The observers who were to man the ground receiving stations were to be drawn from workers at Worth Matravers, near Swanage, to which the Telecommunications Research Establishment, which had started as the Air Ministry Research Establishment at Bawdsey, had been evacuated after a short stay in Dundee. The observers for the aircraft search were to come from the R.A.F. ‘Y’ Service.
On 18th June we briefed Bobbie Blucke and on the following day a search aircraft was in the air for the first time; but neither on that day nor 20th June was anything like a beam detected. This was slightly discouraging, but things done so hurriedly rarely work the first time.
There had to be two beams. One, I was reasonably sure, was at Cleves although our photographic reconnaissance was not yet adequate to find it. Felkin soon gave me the site of the other, for he found it on a paper salvaged from an aircraft shot down in France. This said:
1. Knickebein (Bredstedt no. ö Husum)
54°39’
8°57’
2. Knickebein
51°47’5”
6°6’ (b. Cleve)
This fixed the second beam transmitter up in Schleswig Holstein: and another paper, this time from an aircraft shot down on 18th June gave ‘Knickebein, Kleve 31·5’—which confirmed Scott-Farnie’s guesses about the frequency. And on 21st June another paper gave us the frequency of the Schleswig Holstein beam as 30·0 megacycles per second.
One problem remained nagging in my mind: were Knickebein and the X-Gerät one and the same thing? On 20th June Felkin was told by a new prisoner that the X-Gerät was a bombing system which involved intersecting radio beams. This description exactly fitted what we now knew of Knickebein, but I determined to keep open the possibility that there were actually two different systems using the same principle. But long before that problem could be solved, much was to happen.
On the afternoon of 20th June, I heard rumours that there was to be a meeting the following morning at 10 Downing Street about the beam situation. But since no one had asked me to attend, and I could not very well push myself, I decided to go on with my work in a way that, although enormously more hectic than it had been ten days before, was now normal. In fact, the only surviving feature of my pre-beam routine was that I did not get into my office before 10 o’clock. There was little point in being earlier, because the night’s incoming messages were hardly ready before then, and it was more sensible to start late-ish and work into the evening. So I caught the train from Richmond on 21st June at about 9.35 a.m. as usual, and arrived in my office at ten past ten. On my desk was a note from Daisy Mowat: ‘Squadron Leader Scott-Farnie has telephoned and says will you go to the Cabinet Room in 10 Downing Street.’ Well, in view of our lighthearted office relationships, it could just have been a joke, and so I checked with Daisy and Scott-Farnie before taking a taxi round to No. 10. I arrived at the Cabinet Room some twenty-five minutes after the meeting had started.
I hardly knew what to expect. As I was shown into the room through double doors (they can be seen in Plate 4(b)) I had an end-view of a long narrow cloth-covered table with a writing pad and blotter set before each place, and racks of black-embossed Downing Street notepaper distributed along the table. Churchill was sitting in the middle of the left side, his back to the fireplace; he was flanked by Lindemann on his right and Lord Beaverbrook on his left. Everyone else was sitting on the other side. Immediately opposite was Sir Archibald Sinclair, who had recently become Air Minister, and who was flanked by the most senior officers in the Air Force: Sir Cyril Newall, Chief of Air Staff, Sir Hugh Dowding, Commander-in-Chief of Fighter Command, Sir Charles Portal, Commander-in-Chief Bomber Command, and Sir Philip Joubert, nomi
nally the Adviser on Combined Operations, but in fact in charge of all radar and signals matters in the Air Force. Sitting with them were Tizard, as Scientific Adviser to the Air Staff, and Watson-Watt as Scientific Adviser on Telecommunications. There were no secretaries, perhaps because the matter was so secret.
Immediately, I encountered a problem: the atmosphere was clearly tense and perhaps even that of a confrontation, and I stood for a moment waiting for an invitation to sit down. Lindemann waved for me to go to sit beside him, and at the same time the Air Staff beckoned me to sit with them. Lindemann was my old professor, and was probably responsible for my being there, but my post was with the Air Staff. I saw that I could conveniently resolve this conflict of loyalties by sitting in the chair nearest the door, which was in the ‘no-man’s-land’ at the end of the table between the two sides; and so there I sat, somewhat isolated—the chair is visible to the left of Churchill’s shoulder in the photograph at Plate 4(b).
Churchill’s subsequent description of the meeting in Their Finest Hour was not quite correct, for he said there that ‘according to plan’ he invited me to open the discussion. Actually, it must have already been in progress for some 25 minutes when I arrived, and I listened for a time while some of those around the table made comments which suggested that they had not fully grasped the situation; only then did Churchill address a question to me on some point of detail. Instead of dealing with it, I said, ‘Would it help, sir, if I told you the story right from the start?’ Churchill seemed somewhat taken aback, but after a moment’s hesitation said, ‘Well, yes it would!’ And so I told him the story. The fact that my call to the Cabinet Room had been so sudden had given me no time to rehearse, or even to become nervous. The few minutes of desultory discussion that had ensued after my entry showed me that nobody else there knew as much about the matter as I did myself and, although I was not conscious of my calmness at the time, the very gravity of the situation somehow seemed to generate the steady nerve for which it called. Although I was only 28, and everyone else around the table much my senior in every conventional way, the threat of the beams was too serious for our response to be spoilt by any nervousness on my part.
Churchill himself recorded that I spoke for some twenty minutes, which is quite a time to have the Prime Minister listening at the height of the greatest crisis that had ever confronted the country. He went on to say: ‘When Dr. Jones had finished there was a general air of incredulity. One high authority asked why the Germans should use a beam, assuming that such a thing was possible, when they had at their disposal all the ordinary facilities of navigation. Above twenty thousand feet the stars were nearly always visible. All our own pilots were laboriously trained in navigation, and it was thought they found their way about and to their targets very well. Others round the table appeared concerned.’
Again, I sensed that Tizard had perhaps overdone his scepticism about the beams, but Churchill asked me what we could do. I told him that the first thing was to confirm their existence by discovering and flying along the beams for ourselves, and that we could develop a variety of countermeasures ranging from putting in a false cross-beam to making the Germans drop their bombs early, or using forms of jamming ranging from crude to subtle. Churchill added all his weight to these suggestions. In addition, he said that if the Germans were to fly along beams, this would be the ideal case for our sowing fields of aerial mines, which he had been pressing on the Air Ministry for some years, adding as he angrily banged the table, ‘All I get from the Air Ministry is files, files, files!’ And then the meeting ended. There were no minutes, because the matter seems to have been deemed so secret that no secretaries were present, and the only record was the one that I made for my report written during the following week. After the meeting, Archibald Sinclair came across to me and introduced himself, adding that he understood that I was working with his old friend, Stewart Menzies in M.I.6.
I returned to my office much elated at having convinced the Prime Minister. My elation, however, was to be dashed by the events of the afternoon. There was a conference in the office of the Director of Signals, Air Commodore Nutting, to discuss the possibility that the Germans might exploit pulse transmissions as navigational aids over this country, and on which Mr. T. L. Eckersley was to give evidence. The meeting, however, reverted to Knickebein, because Eckersley wanted to give instead his views on how wrong I was about it. It will be remembered that he had been given the Kleve message by Group Captain Blandy on 13th June, and he had interpreted it for himself. He said that it could not refer to a beam and that ‘Kleve’ might well be an error for ‘Klebe’, which meant ‘to stick’ and that the message might well be an instruction to paratroops to ‘stick like glue’ to position 53° 24’ north 1° west. When I asked him why he rejected the idea of a beam, he said that a short-wave beam from Cleve could not possibly be heard at twenty thousand feet in England—it would just not bend sufficiently round the earth. If this were true, it would completely destroy my case and, ironically, it was on the basis of Eckersley’s earlier calculations that I had demolished Lindemann’s objections and thus succeeded in raising the alarm. I reminded Eckersley of his calculations, which contradicted what he was now saying: he replied that I ought not to have taken them seriously, what he was doing then was to calculate how far they might go under some circumstances, and that he did not believe them himself. And to support his argument there was the fact that our aircraft had failed to detect any beams on the two preceding nights.
At that point the principal Deputy Director of Signals, Group Captain O. G. W. G. Lywood said something like, ‘Well we now have the greatest expert on radio propagation in the country and he says that the beam theory is all wrong. We have wasted a lot of effort and let’s not waste any more. This evening’s flight should be cancelled!’ I weighed up my position, and pointed out that Eckersley’s evidence had neutralized itself, because he had said one thing a few months before and now something quite different. In that case I proposed that his statements should be ignored, and that I already had so much other evidence that I was convinced that the beams existed. I told Lywood that if he cancelled the flight, which I myself had heard the Prime Minister authorize that very morning, I would see that the Prime Minister came to know who it was who had countermanded his orders. This was a strong line to take, but it was a case of risking all; Lywood backed down and the flight plans went ahead. I was asked where the aircraft should search, and I suggested that we should assume that the director beam was on Derby, because the most crucial target in England at that time was the Rolls Works where the Merlin engines for Spitfires and Hurricanes were made.
I also gave the expected frequencies on which the aircraft should search, and it was arranged that it should take off from Wyton in Huntingdonshire to fly northwards so as to cross the beams. From the chair, Nutting said, ‘And what do we do if we find the beams?’ Quietly I whispered to Scott-Farnie, ‘Go out and get tight!’ At the end of a long day I went home and spent a thoroughly uneasy night. Had I, after all, made a fool of myself and misbehaved so spectacularly in front of the Prime Minister? Had I jumped to false conclusions? Had I fallen for a great hoax by the Germans? Above all, had I arrogantly wasted an hour of the Prime Minister’s time when Britain was about to be invaded or obliterated from the air?
Fortunately, this period of wretched introspection was dispelled the next day when the results of the search flight were reported. We held a meeting in Joubert’s room in the afternoon, and the pilot, Flight Lieutenant H. E. Bufton, was there to tell us what he had found. Neither he nor the observer, Corporal Mackie, had been told the Knickebein story, but merely to search for transmissions with Lorenz characteristics and to locate the equi-signal line after taking off from Wyton and flying northwards. His flight report read:
(1) That there is a narrow beam (approximately 400–500 yards wide), passing through a position I mile S. of Spalding, having dots to the south and dashes to the north, on a bearing of 104°–284°T.
&n
bsp; (2) That the carrier frequency of the transmissions on the night of 21/22 June was 31.5 Mc/sec. modulated at 1150 cycles and similar to Lorenz characteristics.
(3) That there is a second beam having similar characteristics but with dots to the north and dashes to the south synchronized with the southern beam, apparently passing through a point near Beeston on a bearing lying between 60° + and less than 104°.
The guess about Derby proved a good one, at least in anticipation. The diaries of the German Chief of Air Staff, Ernst Milch, for 21st July show that Goering thought that air supremacy ‘could be achieved only by destroying the R.A.F. and its supporting aero-engine industry—an industry the enemy would be forced to defend.… As to their tactics, Goering suggested they should make these factories the targets for nuisance raids by night at once.’
The impact of Bufton’s brilliant report on the meeting was all that might be expected. Our conclusions had been confirmed: there were indeed two beams, whose bearings were consistent with transmitters at Cleves and Bredstedt. There was even jubilation: I can recall ‘Daddy’ Nutting—who, I felt, was always on my side, even in the bitter disagreements that I had with some of his staff—actually skipping round the room in delight. All doubts were now removed, and plans for counter-measures could go urgently ahead. As our meeting ended Rowley Scott-Farnie said to me, ‘Remember what you said yesterday?’ and so he and I went across to St. Stephen’s Tavern, on the other side of Whitehall, to indulge in a celebration that was tempered only by the knowledge that I had to drive down to Boscombe Down on the following day to take some equipment for chasing fifth columnists.
