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At the outset, Tizard and his Committee—and Britain—had a tremendous stroke of luck, for on 18th January 1935 Wimperis saw R. A. Watson-Watt of the Radio Research Station at Slough, and asked him to advise ‘on the practicability of proposals of the type colloquially called “death ray” ’, the idea being the creation of a sufficiently strong beam of electromagnetic waves which would heat up anything in their path to the point where living tissue would be destroyed or bombs automatically exploded. Watson-Watt had given the problem of calculating the amount of power employed to his assistant A. F. (‘Skip’) Wilkins, and the latter quickly calculated that the power involved would be far beyond current technology. When he handed the calculation to Watson-Watt the latter said, ‘Well, then, if the death ray is not possible, how can we help them?’ Wilkins replied that he knew that Post Office engineers had noticed disturbances to radio reception when aircraft flew in the vicinity of their receivers, and that this phenomenon might be useful for detecting enemy aircraft.
The Post Office observations had been made in 1931, and indeed rather similar observations had been made at H.M. Signal School in 1923. Moreover, Marconi had proposed in 1922 to detect ships by means of reflected radio waves and in 1931 W. A. S. Butement and P. E. Pollard of the Signals Experimental Establishment at Woolwich had devised and made a pulsed radio system on a wavelength of about 50 centimetres for detecting ships, and a rather similar system was in course of being installed on the French liner Normandie for detecting icebergs. As regards air defence in Britain, though, it was Wilkins’ remark to Watson-Watt that started the serious development of radar.
A brief note from Watson-Watt was available to the Tizard Committee at its first meeting on 28th January 1935 and by 14th February Tizard had received a more detailed memorandum. On 26th February the first test was held near Daventry, using radio waves from one of the transmitters there in the 49 metre band, and with a Heyford bomber as a target flying at a height of ten thousand feet and piloted by Squadron Leader R. S. Blucke. The test was immediately successful, and the British development of radar could now start in earnest. So from the very first, the Tizard Committee had been presented with the basic solution to the greatest of the problems that it had to face.
On the same day, 14th February, that Tizard had discussed with Watson-Watt and others over lunch at the Athenaeum the paper Watson-Watt had produced, Lindemann and Churchill were joined by Austen Chamberlainin meeting Ramsay MacDonald, who finally agreed that an air defence sub-committee of the Committee of Imperial Defence should be formed, notwithstanding the existence of the Tizard Committee. It appears from Lindemann’s notes that the Prime Minister even agreed to get the Tizard Committee wound up. The C.I.D. Sub-Committee met for the first time on 11th April under the Chairmanship of Lord Swinton, who suggested that Churchill should be made a member. Churchill agreed, provided that Lindemann would be made a member of the ‘Technical Sub-Committee’, which was how Churchill regarded the Tizard Committee.
I knew very little of all this, and was brought into the field in a manner which involved neither Lindemann nor Tizard. It started with a ring on the bell of my lodgings at 10 St. Michael’s Street on the morning of Saturday 16th February 1935. My landlady informed me that I had visitors, and these turned out to be Commander Paul H. Macneil, a retired officer of the U.S. Navy, and his wife, Ruth. They had come to England in the hope of selling to the Air Ministry a detection system for aircraft based on the infra-red or heat radiation emitted by aircraft engines. They were due to give a demonstration at the Royal Aircraft Establishment on the following Thursday, and at the last moment the vital detecting element in their apparatus had broken down. Resourcefully, Macneil had contacted the Institute of Physics in London and asked whether there was anyone in England who could make him a replacement detector in a hurry.
It happened that a few months before I had published a paper on the design of infra-red detectors, and the Institute of Physics suggested that Macneil should get in touch with me. I was fascinated with Macneil’s ideas, and told him that I would try. I thought that at worst I could only waste four days of my life, because he said that it would be no good unless the detector could be made by Wednesday evening. I therefore evolved a new design on Sunday, and spent the next three days and nights with very little sleep, only to fail. At about 2 a.m. on the day fixed for the trial I telephoned Macneil to tell him that I had failed, but he replied that this did not matter because the trial had been postponed for a fortnight, so perhaps I would try again. Over the next few months I saw a good deal of the Macneils in their flat above Prunier’s, from which we viewed the 1935 Jubilee Procession. I was with Macneil at Croydon aerodrome at about this time when he undoubtedly detected the Imperial Airways aircraft as they taxied for take-off.
So at just about the same time that radar was at the nascent stage, I became involved with infra-red at a similar stage. Lindemann did not come into my room for a week or two; but when he did, and asked me what I was doing, I told him that this very interesting job had come up, and that I was seeing what I could do to detect aircraft by infra-red. His immediate comment was ‘You ought not to be doing that for an American inventor, you ought to be doing it for the Government!’ He went on to say that he had proposed the idea himself in 1916 but that no one had done anything about it. Unwittingly, I had presented him with an argument that he could use against the Tizard Committee, for he could now say that while Tizard and his friends were sitting around a table talking, he, Lindemann, had a man in his laboratory actually doing something about air defence. Towards the end of April I had a long talk with him, and as a result he may well have begun to press for something to be done officially about infra-red, for the minutes of the Tizard Committee for 16th May contained the following entry: ‘The Committee considers that the detection of heat radiation from an aircraft engine or of energy radiated by an aircraft engine magneto offer no prospect of success; each of these methods has been the subject of experiments’. Indeed, A. B. Wood, a distinguished physicist on the Admiralty staff, had made trials with infra-red at Farnborough in 1927 which indicated that infra-red was unpromising, and his findings could be supported by the argument that the infra-red radiation coming out of an aircraft engine could easily be screened by an extra cowling, and that even if it did get out, it would not penetrate cloud. Finally, whereas radar gave an indication of the range as well as the direction of the target, infra-red could at best give direction only.
As usual when faced by opposition, Lindemann produced a plausible counter-argument. Although engines could be screened, there was far more heat energy coming out in the exhaust gases than that which would be radiated by the engine, and these gases, too, would radiate and so they should be detectable. To satisfy Lindemann the Committee then agreed that some trials should be made at Farnborough. The trials were to be undertaken by an impartial body, the National Physical Laboratory, but even then Lindemann said that he would only accept them if I were present as an expert observer on his behalf. I was therefore surprised when Dr. J. S. Anderson of the N.P.L. telephoned me and asked if he could borrow my infra-red aircraft detector. He explained that the N.P.L. had no suitable equipment but that Mr. Wimperis had told him that Lindemann had said I had an infra-red detector which flashed lights whenever an aircraft flew in front of it. I explained that I had no such thing and Anderson seemed so crestfallen, saying he now had no hope of doing the trials, that I offered to help him out by at least making a detector that should be capable of settling the point about exhaust gases.
I realized that Lindemann had made what I subsequently came to recognize as a characteristic overstatement. I had sometime before told him that, from what I had seen of Macneil’s experiments, it should be possible to make a much better system by oscillating the detector mirror so that any hot source in the field of view was alternatively focused on and off the detector element, giving rise to a rhythmic signal which could easily be recognized against its background. For this a fast detector would be requ
ired, and if one could be made its rhythmic fluctuations could be used to generate an alternating current which could be amplified electronically, rather than detected by a galvanometer. Once we had the possibility of electronic amplification, we could begin to give visual warning of the presence of an infra-red source, and could even make a pattern of lights which would indicate the direction of the source. These were all ideas that I considered feasible but which no one had pursued, and which Lindemann must in his mind have converted into a fictitious reality before he told the other members of the Tizard Committee about them.
There would be no time to build such an apparatus before the Farnborough trials. So I spent most of October 1935 making something much simpler that should resolve the question Lindemann had raised. On 4th November I set the equipment up on the roof of the Instrument Building at Farnborough to examine aircraft suitably staked on the ground as their engines were raised to full revolutions. Whereas Anderson was to have done the trials and I was to have been the observer, our roles were reversed. It quickly became evident that although there was ample infra-red radiation being emitted by a hot engine, this could be easily screened, and by interposing a movable aircraft spare wing in front of the engine I showed that there was little infra-red getting out from the hot gases in the exhaust. After a few days I returned to Oxford and wrote the report, sending it to Anderson for his agreement before I showed it to Lindemann. The latter was understandably annoyed that he had had no chance to question our findings before they had received the authority of the National Physical Laboratory, but I thought that this would be the end of the matter. His argument had been so plausible that there must be a factor he had overlooked: this turned out to be the fact that the gases had indeed radiated infra-red as he expected, but they radiated it in the very bands of wavelength that are strongly absorbed by the carbon dioxide and water vapour in the Earth’s atmosphere, and so become almost undetectable at more than very short ranges. With current technology, as opposed to that of forty years ago, the small amounts of energy that do get through can now be detected, and in any event engines are much more powerful and therefore emit much more, but the exploitation of the technique lay far in the future.
My report to the Tizard Committee had the opposite effect to that which I expected. Instead of the Committee deciding that nothing further should be done about infra-red, they asked me to see whether I could develop an airborne infra-red detector so that it could be mounted on a nightfighter and thus detect bombers. Quite possibly their engines would not be screened, and quite often they would be flying in clear conditions without cloud; and although airborne radar was possible, it might not work at short ranges owing to the fact that the pulse coming back from the bomber would be swamped by the pulse still emitted by the fighter. There could thus be an awkward gap in the interception technique over the last thousand yards or so, which infrared detection might fill. It seemed that the Tizard Committee had been so surprised by the objectivity of the report coming out of Lindemann’s laboratory that they were ready to support further work there.
CHAPTER THREE
The Clarendon Laboratory
1936–1938
MY WORK on the airborne infra-red project was to start on 1st January 1936, and I was to receive an honorarium of £100 for four months’ work and an extra £50 for equipment. If the latter seems a paltry sum now, it was large compared with what many of us in laboratories in the ’30’s were accustomed to. And since these laboratories were the cradles for most of the scientists who were later to contribute so substantially to World War II, it may be worth giving some impression of the Clarendon as a typical laboratory.
When Lindemann took it over in 1919 it had long been moribund. Perhaps because he had found his activities in World War I so absorbing, he never again settled down to serious research, although with F. W. Aston he proposed a method of separating isotopes, and with G. M. B. Dobson diagnosed the existence of a high temperature layer in the upper atmosphere, and with T. C. Keeley devised a new form of electrometer. These were the most successful examples of the diversity of his mind, and he started off his relatively few research students over a wide range of projects where they had no expert help, so it was very much a matter of ‘sink or swim’ for them. Two or three graduates would start research each year, and roughly the same number leave after two years; since there were no more than six Fellowships in physics in the whole university, there was little chance of one of these becoming vacant for a new worker to fill. The Cavendish under Rutherford at Cambridge obviously had much greater attractions for serious physicists, and so for Lindemann’s first fifteen years he had rather an odd assortment to choose from. Even so, his was a lively laboratory where not only was good physics done but also its fifteen to twenty members had a number of other achievements to their credit. Derek Jackson, later to be Chief Airborne Radar Officer in Fighter Command, for example rode in the Grand National. James Griffiths, subsequently President of Magdalen, was a member of Leander. Two others, ‘Snooks’ Gratias and Jack Babbitt, were ice hockey blues, and Hylas Holbourn was Laird of Foula in the Shetland Islands. And for some years T. C. Keeley and E. Bolton King made the best photoelectric cells in the world.
It is not clear how long it would have taken the Clarendon to establish its reputation unaided, for in 1933 there occurred the exodus of Jewish and other scientists from Germany, and Lindemann was among the first to offer them refuge. We thus had an invigorating influx of physicists including Erwin Schrödinger, the London brothers, Leo Szilard, Franz Simon, Nicholas Kurti and Kurt Mendelssohn; especially in low temperature research they rapidly advanced the Clarendon to a world reputation.
By way of technical help, we had just two mechanics in the workshop, A. H. Bodle and W. Stonard. I owed much to both of them. Bodle lived with his wife and daughter in a lodge just outside the laboratory, and I was often invited in for a late night cup of tea. Frequently in the evenings would come the sounds of trios being played with Mrs. Bodle at the piano, Marion with the violin and Bodle with the viola. Physically a little man with Napoleon as his hero, Bodle had largely taken refuge in books as an escape from the buffeting of the world. He urged me not to remain as uneducated as he believed the typical physicist to be, and he recounted with awe once hearing Lindemann quote Herodotus. I promptly read Herodotus, and was impressed by his penchant for good stories, and with his honesty as an historian when he told that, while he himself found it hard to believe, the Phoenicians who claimed to have sailed round the south of Africa said that the sun then rose on the other side. This observation simultaneously established Herodotus as honest and added to the credibility that the Phoenicians had really gone as far south as they claimed—a point of narrative technique that I was later to use in trying to get the Germans to accept some of our deceptions as genuine. Encouraged by Bodle I went on to read Plutarch and Thucydides, and even the Icelandic Sagas, all of which were to be sources of inspiration during the coming war.
Besides the Jewish refugees, we now had a German physicist of much my own age, Carl Bosch, working in the laboratory. His father was also Carl Bosch, a very fine man who had shared the Nobel Prize in 1931 for high-pressure chemistry. He was President of I.G. Farben Industrie, and his prestige was so great that he was elected by his fellow scientists as President of the Kaiser Wilhelm Gesellschaft, as one of the few men big enough to stand up to the Nazis.
I first heard about Bosch from some of the others in the Clarendon, who told me that he was a great practical joker. There was something challenging about their tone, and I wondered whether they had said similar things about me to Bosch, with the object of getting us to play practical jokes on one another. Fortunately for me, and perhaps unfortunately for the rest of the Clarendon, he happened to be in the Laboratory a few evenings later. Since ‘the Prof’ himself tended to set the pattern by not arriving before 11 a.m., not a great deal of work was done during our mornings, and it was customary for a few of us to come back after dinner and work well past midnight
, and sometimes all night. On this particular evening when Bosch and I first met, we started to chat and the subject worked round to the tricks that one could do with a telephone. Bosch told me that he had worked on an upper floor of a laboratory from which he could see into the windows of a block of flats, and he had found that the occupant of one of them was a newspaper reporter. The telephone in the flat was visible through the window, and Bosch telephoned the reporter pretending to be his own professor. He said that he had just invented a marvellous instrument that could be attached to any ordinary telephone, and which would enable the user to see what was going on at the other end. This was around 1933, when the possibilities of television were just being mooted. The reporter was, of course, incredulous, and the supposed professor offered to give him a demonstration. He told the reporter to point the telephone towards the middle of the room and to stand in front of it and assume any attitude he liked, such as holding one arm up, and when he returned to the telephone he would be told exactly what he had done. Bosch, of course, could see perfectly well what he had done simply by looking through the window. The reporter was appropriately astonished, with the result that the following morning there appeared a most enthusiastic article about Bosch’s professor and his marvellous invention, together with a detailed description of the demonstration.
Bosch and I then happily discussed variations on the telephone theme and ultimately I said that it ought to be possible to kid somebody to put a telephone into a bucket of water. I outlined to Bosch the various moves, and we were laughing about the prospect of their success and wondering whom we should select as a victim when one of my colleagues, Gerald Touch, came into the Laboratory and asked why we were so amused. He shared our amusement at the prospect of the bucket of water, and he offered to return to his digs, where several research students resided, and to watch while one or other of them answered the telephone, so as to report whether my plan had been successful.