During the summer of 1937 John's practical PhD work was coming to an end and, although Reinet's research would not finish until the end of the year, both started to think about finding work. Reinet was offered a job as Secretary to the Association of Scientific Workers (ASW, later AScW) in London at £ 250 a year and, sure that her performance at Cambridge did not point to a scientific career, she was inclined to accept. John was invited to apply for three jobs in the electrical industry. To be reasonably near to Reinet, he accepted an offer of five pounds fifteen shillings a week from Standard Telephones and Cables (STC) at Woolwich.At this stage it is interesting to speculate on what might have happened to John's career if his abilities as both a practical and a theoretical scientist had been appreciated earlier, or indeed if he had simply worked harder as an undergraduate. Had he been given a first, he would probably have been one of those chosen by Lord Rutherford to do a project on radioactivity for his PhD. After that he would automatically have been asked to stay on at Cambridge, and from there it would have been a short step to Los Alamos to work on the first atomic bombs. Had this happened, John told me, he would not at the time have viewed it as so terrible, for the science behind nuclear fission was new and he found it fascinating. The British scientists who did join in the work in America were excited by it and at the same time convinced by Einstein who believed that Germany was working on an atomic bomb and that America must be made to produce one first. Later John felt desperately sorry for scientists who had been drawn into such work by following this route.
John was due to start work with STC on the first of October 1937. With a reasonable income in prospect, he felt able to get married and so on 11th September the wedding took place at West Malling Registry Office. Reinet wore a powder-blue suit (which she dyed dark blue a month afterwards for Lord Rutherford's funeral) and Celia made the wedding cake and arranged the reception at Heavers. John took the wedding photograph using the delayed action device on his camera.
John had arranged a stay at Yenworthy farm in the Doone Valley area of North Somerset for a honeymoon. In preparation for a walking holiday, he had a stout pair of walking shoes specially made by a West Malling cobbler. These shoes had such thick soles that when wearing them with shorts John looked like a certain cartoon character and so the shoes were nicknamed his 'Mickeys'; Reinet's lighter shoes then had to be christened 'Minnies'. To Celia's astonishment, John and Reinet prepared further for their honeymoon by packing notes, a typewriter and the shorthand Reinet was attempting to learn. This was not done because they expected to get bored with one another, but John had read novels where the plot depended on difficulties that could arise when honeymooners had nothing to do if it rained all the time, and didn't see how they could be sure of being different from everybody else.
The typewriter never came out of its case, and the shorthand remained unpractised. John and Reinet had a wonderful time exploring the countryside, in reality a more rolling, less rugged area than that described in 'Lorna Doone' and ideal for a walking holiday, dotted as it was with farmhouses offering cream teas. They carried their lunch with them on their expeditions and sometimes gave themselves a challenge to add interest: one day they decided to try and find the source of the River Exe, wondering if it would be a spring, and using the map to get as close as possible. When they found themselves sinking into a marsh, they decided they had found it!
One day John strained his knee, and they had to go uphill to catch a bus. Experimenting, he found that it was more comfortable to trot up the hill than to walk, and poor Reinet struggled to keep up while carrying his rucksack. The next day he had to sit and wait while Reinet picked up their daily supply of chocolate and as she walked down the hill to the village and he lost sight of her for the first time since they were married, he thought about how awful it would be if she never reappeared.
After two weeks they returned to Ryarsh with less than a week left before John was to start work. Reinet still had a term to go at Cambridge, so John decided to take temporary lodgings within reach of STC. They had been advised that a good place to look would be in Charlton, across the Thames from North Woolwich, so they walked up the bus route from South Woolwich along a road of look-alike small houses. They didn't have any luck at first knocking at doors at random, until it occurred to John to look for a house with an aspidistra in the window. Sure enough, the door of the very first such house opened to reveal a nice old lady happy to offer him bed, breakfast and an evening meal from Sunday evening to Friday morning each week.
Nearly all industry at this time operated on Saturday mornings but John was in luck, finding that STC worked until quarter past six on four days a week to give the non-manual staff what was then a long weekend starting at half past five on Friday. This meant that John could catch a train into London and another to Cambridge each Friday evening to be with Reinet for the weekend.
This was an unconventional start and neither enjoyed the separation. However, respect by each for what the other wanted to do was one of the cornerstones of what turned out to be a very strong marriage. Unfortunately, Reinet found that her grant from the Beit Fellowship did not allow the holder to be married, but after writing and telling her sponsors that they were encouraging living in sin, she settled down to cope for the one term on the money from Cape Town University and some savings she had managed to accumulate.
John started his journey from his lodgings to STC by catching a bus to the south of the river. Buses at that time had no doors, and he found that he could get on a bus going uphill if he grabbed the hand column as the bus caught him up, and jumped at just the right moment. After the bus ride he had to go along the footway tunnel across the river, reached at each end by a spiral stairway of over 60 steps. He soon got very skilled at taking the stairs three at a time and would sprint along the tunnel in between, although it could be crowded, which slowed him down. To avoid these tricks by setting out a few minutes earlier would not have been an acceptable solution for he could always find something more important to do with spare time, and he probably enjoyed the dull journey more by turning it into a challenge to defeat the system.
John found that most of the group he was joining had been there for only a few weeks. It turned out that this was because the parent company (International Telephones and Telegraphs) in the United States had instructed STC to sack its team of scientists at the beginning of the recession. At the end of the slump, STC was told to re-employ the same people but they had of course already been snapped up by less short-sighted companies. One of the others taken on at the same time was Douglas Petrie. John and Douglas worked with Philip Parker and a Dutchman called Wolsey under Mr Gibson, an electrical engineer. The group included two mathematicians, A W Gent and Peter Wallis and there were in addition two technicians, Roger Hall and Tom Jakes and a glassblower. Dr Black was head of research.
John had been taken on by STC to work on electronic valves for radios. Valves have now been made almost obsolete by transistors, but they used to have a wide variety of commercial applications including broadcasting and receiving radio waves. Alterations to the parts of a valve can result in all sorts of different functions and different levels of performance, and it was obvious to those in the electrical industry of the time that there were still vast opportunities for the production of improved models.
The simplest valves (diodes) each consist of a positive anode-1- and a negative cathode-2- in an evacuated tube. If the cathode is heated, it evaporates electrons into the space inside the tube. These electrons then assist a current to flow in only one direction when the tube is connected into an electric circuit and a diode has been described as a one-way street for electrons. The valve can then act as a simple switch or as an amplifier. Other valves are made more complex by the addition of grids between the anode and cathode.
John and Douglas's first job was to examine a formula that already existed to calculate the current per square centimetre of cathode under a variety of different conditions, but which did not work for all types of valve. Douglas settled down to some theoretical calculations, while John designed a system for moving a flat grid and a flat anode by placing them on steel carriages running on steel rails. This equipment would be able to simulate various valve layouts once it was fitted under a bell-jar that could be evacuated. This all took the workshop several months to build, so meanwhile John decided to set up a stretched rubber sheet model.
This model had been designed to demonstrate the working of valves. If a sloping rubber sheet is stretched, and then has various objects placed underneath it so that they push it into a number of hills and valleys, balls that are rolled down it can represent the flow of electrons from cathode to anode under the influence of the various parts of a valve. To this existing set-up, John added a fresh feature: he illuminated the sheet from above with a fluorescent lamp that emitted a brief flash of light every fiftieth or hundredth of a second. Then he fixed a camera to the ceiling, focused on the whole area of the sheet and put it on a time exposure just before a number of balls were released from the 'cathode'. When he developed the film, the track of each ball showed up as a dotted line, the distances between dots showing the changing velocity of the ball as it travelled along its path. John examined every part of the rubber sheet demonstration from the deterioration of the rubber in sunlight to the optimal amount of stretch to give meaningful results (which he found to be thirty percent), and within a year had so refined the set-up that it could be used as a method of actually determining the outputs of various types of valves, and at the same time produced a reason for the as yet unexplained behaviour of pentode-3- valves.
When the system for a grid and anode on moveable steel carriages at last appeared, there was a hiccup when the carriages refused to slide once the bell jar that housed them was evacuated, and John decided that air must usually act as a lubricant when two pieces of steel move against one another. Changing the steel rails for brass solved the problem. Using the comprehensive experimental results from this apparatus to confirm his and Douglas' mathematics, he produced a reliable method of calculating the current flowing in a triode-4- valve. A paper describing these efforts was duly published in the Philosophical Magazine entitled 'Calculation of Triode Constants' in June 1939, which started by pointing out that previous formulae had been obtained simply by reference to information already known about diodes.
Returning to 1937, the time came for Reinet to leave Cambridge in December, and the Fremlins found a flat on the top floor of a block in Holborn, which took nearly a quarter of their joint annual income. Their coal cellar was under the pavement, and coal had to be carried up ninety steps. John put a galvanised iron container in their kitchen and filled it every weekend, making multiple trips up the stairs with a loaded rucksack.
The move increased the length of John's journey to work and although he did his best to pare it down to the bare minimum, the journey still took an hour or more. In the spring he reduced the time the journey took by starting to cycle but did not continue the next winter after deciding that wet, tramline-pitted roads were too dangerous in the dark. Reinet would arrive home from her job in Earls Court at about quarter past six. Although she had never cooked anything other than cakes and puddings before (she took John along to the butcher's shop with her the first time she went to buy meat), she soon became expert at cooking the evening meal in half an hour to be ready when John got home soon after seven o'clock.
When John left Cambridge, he was given a year in which to present his thesis for his PhD, and he worked on this in the evenings. After describing his experimental work he had to present a discussion of the way it fitted with previous theories, and in the case of the gas-discharge experiments, he could not find an exact fit with any of them. After hunting for flaws in the assumptions in the latest theory, he got down to examine the detailed mathematics, and to his surprise, came across an elementary-5- mistake (a missing constant of integration). Hardly daring to trust himself, he handed the suspect lines of mathematics to Reinet, asking only if she could see how their author got from one line to the next, and Reinet spotted the same error independently. Processing the extra calculations that resulted from altering the offending lines was a formidable task, but produced an improved theory that matched John's results nicely.
Once the thesis was written and Reinet had typed it, there was an oral examination, and Dr Oliphant took the part of the senior internal examiner. The most difficult question he asked was: "what do you think of Gunterschulze?" Cavendish students were expected to have a working knowledge of technical German but John's studies in German had been sadly neglected. Instead of reading Gunterschulze's original papers, he had studied the graphs, which hadn't seemed to explain anything much, but he had included the papers in his list of references anyway. To answer Oliphant's question, he said simply that he had found Guntherschulze of little help, and this seemed to be accepted as the right answer. Needless to say, John obtained his PhD with no trouble at all. After the interview, he was gratified when Oliphant asked him if he would write a monograph on gas discharges because, he said, John had given quite the clearest explanation of the cathode region that he had seen.
And what of Reinet's thesis? She had left Cambridge with the feeling that she had followed instructions adequately, but had done nothing particularly interesting or original. Once she was married and working, she became so busy, that even if she had been motivated more strongly, she would have found it very hard to do any writing up of her own. She moved instead towards a supporting role, enjoying helping John by typing his work and producing neat tables and graphs.
Maintaining their old interests, they joined the London Scientists Anti-war Group, and often housed its meetings in their flat, as it was central. This organisation managed to stimulate some media interest in the inadequacy of the government's stockpiled civilian gas masks, and the Daily Express invited John to test the masks. The reporter O D Gallagher (who became a war correspondent and was killed during the war) found a suitable room and obtained a number of the standard civilian gas masks at two shillings and sixpence each. John let off some of the same arsenical smokes he had used before, and fourteen volunteers, including Lord Forbes, Gallagher and Reinet, wore the masks and stayed in the room as long as they could, but most were forced to leave before the end of the ten minute test, some in a state of collapse. Gallagher wrote his report and then allowed John to check it. It appeared as headline news in the Daily Express of 17th August 1938, with half the back page devoted to photographs. The Home Office had refused an invitation to attend the test, but six months later an improved gas mask was produced.
Annual leave did not build up as quickly in the 1930's as it does today, and John had to make the best of one week and bank holidays for his first year at work. By 1939, however, John had accumulated two full weeks of leave and they decided on a cycling holiday in Dorset. As Reinet had been enrolled as an Air Raid Warden and John as a Gas Protection Officer for the Borough of Holborn, they had had to promise to return at once if recalled.
Starting at Yeovil, the young couple cycled along the River Piddle, calling in at Piddletrenthide and Puddletown. They were sitting having morning coffee at Tolpuddle, when they heard over a wireless set the general recall of anyone with any civil defence responsibility. They cycled the twenty miles to Poole station to find it full of people, with no information as to when the next London train was due. When the train did arrive, they made a beeline for the luggage van to get their bicycles on board and then stayed there themselves with thirty other people, together with bicycles, prams and dogs. A lot of people were left behind on the platform. It took until the evening to get to London.
Next morning a neighbour came and told them that war had been declared. Soon an air raid warning siren went, so they put on their armbands and tin hats and went downstairs to tell people to stay indoors or go to the trenches in Bloomsbury Square. But before it became clear that it was a false alarm anyway, a story spread that Chatham had been heavily bombed, and nobody wanted to go to the trenches for fear of missing anything.
They managed to escape the false alarms and returned to work. Not long before, John had been removed from his work on valves for radios, and put in charge of a section working on an entirely new type of high frequency oscillator. The work was top secret, and the team was supposed to be completely ignorant of its objectives. However, John had been keeping up with the technical literature, and he had seen an article written by someone from the Woolwich Arsenal on 'The detection of cosmic ray bursts in the upper atmosphere' using the reflection of high frequency radio waves; no brilliant detective work was needed to guess that the Woolwich Arsenal might be interested in the height above the ground of other objects than cosmic ray bursts! Once John had worked that out, it was obvious to him that accuracy would improve as the radio frequency got larger and so high frequency oscillators would thus be a vital component of a system to detect enemy aircraft. Without discussing these observations with Mr Gibson, John set to work on valves with the high frequencies and short wavelengths required. Almost immediately, his section was moved from Woolwich to a private house in Eltham, for security reasons, taking over an additional house next door shortly afterwards. Although Eltham was further from home than Woolwich, a train service from London Bridge made the journey easier.
John may have been pleased with his knowledge about the cosmic ray burst article, but it is unlikely that he was aware at the time how much work on the detection system that became known as radar in 1942 had already been done. In 1903, Hulsmeyer of Düsseldorf had tried unsuccessfully to make a collision detector using radio and in 1922, Marconi had suggested that the radio waves he was working on could be used for the same purpose. After that time, several countries started their own secret research programmes, Britain forging ahead because researchers were allowed to exchange ideas more freely than in Germany. In 1935 a chain of twenty stations to use the new detection and ranging system along the South and East coasts was proposed, and the first became operational at Easter 1939. Meanwhile, in March 1938, the first airborne radar was working although the screens tended to be full of reflections from the ground. Both these systems used long wavelengths of six to fifteen metres, and were better at detecting whole formations of ships or aircraft then individual vessels. By the time John's section was roped in to join in the work, the search was on to find ways of decreasing the wavelengths and increasing the frequencies used in order to give better discrimination.
For his work on oscillators, John had to be passed by the authorities as fit to be trusted with secret work so he was summoned to the Admiralty to be examined by the security service. The security service turned out to be a slightly embarrassed Naval Officer in a moderate sized room with a screen in one corner obviously hiding a stenographer. He didn't mention the Communist Party at all, but questioned John about his pacifism, concerned that he might refuse to do anything that might involve killing anyone directly or indirectly. Without saying that he knew perfectly well what the object of his current work was, John managed to explain that he had a wife in London and was entirely in favour of doing anything that would stop bombs being dropped on her.
Around the same time, Reinet received a telephone call from Oliphant, who had obviously been recruited to help with John's vetting. Oliphant also asked about John's pacifism, and Reinet explained that she and John both agreed that it was far more important to have Hitler stopped than to avoid war at all costs.
John's communism need not have worried them. The Nazi-Soviet pact negotiated in August so disgusted those who had joined the Communist Party as an anti-Nazi statement, that many, including John and Reinet, soon lost interest and eventually left the party. The ideals of communism, on the other hand, remained important to John for a long time.
Mr Gibson told John that he had been passed 'as of course he had expected'. Previous vetting had been poor: to start off with, John was asked to work with a Dr Heil, who spent more of his time justifying Hitler's actions than actually working; shortly after the war broke out he took off for Switzerland. Scientifically, Dr Heil had appeared a good choice for he and his wife had previously invented a coaxial tube oscillator, the Heil tube, a type of valve that could produce microwave-6- radiation from an incoming electron beam. This tube was based on a short length of coaxial copper tubing with some carefully placed slots. An electron beam directed into the device entered a high frequency electric field. The cyclic nature of such an electric field meant that some electrons accelerated to catch up some of those that went ahead before them but were moving more slowly. This had the effect of bunching the electrons into packets. When these packets hit the next part of the device, a series of grids called the catcher, they gave up energy that was detected as an oscillating field. This method is known as velocity modulation and the resulting microwave energy is used either as the outgoing microwaves of radar or to amplify incoming waves.
To improve upon Heil's original tube, John and Heil wanted to use large electron currents and John designed a water-cooled system capable of handling a kilowatt or more. This system was demountable at this stage so that it could be taken down for the spacings to be experimentally altered. The electrons in a high-current-density beam would repel each other and cause the beam to spread so John decided to set up a large electromagnet to deflect straying electrons back into the correct path.
In the race to get radar functioning, generous funding was offered for any relevant research. Several University Physics Departments, EMI, Mullards and General Electric were also involved in the same sort of work, and team-leaders could obtain funding for any project they could persuade the authorities was relevant. The Admiralty had insisted that companies and academics alike were to share their ideas and developments at regular meetings, but each STC delegate was under strict instructions from his superiors to find out what the others were doing while giving away as little as possible because "you can't trust these people!" Ultimately, this held the company back, for those working in the Universities were successfully sharing information and learning from each other so their work moved forward much more quickly. The development of radar went at an extraordinary pace, and many branches of science were involved in various ways. Even the invention of polythene in 1933 played its part, for here was a material that was not only an excellent insulator, but also flexible and mouldable. By 1941, after a massive organisation to achieve communication between ground stations and aircraft, together with cumulative improvements in performance, enemy aircraft were being shot down at night. At first the British public were encouraged to believe that the most successful pilots owed exceptional night vision to a high consumption of carrots, in the hope that the Germans would believe this too! The speed of development eclipsed the work of individual scientists, but this did not stop each of them putting all he had into his own line of research.
Turning the houses at Eltham into laboratories had not been easy. They had been supplied with power for electric light only but an adequate electricity supply was needed immediately. After Dr Heil had gone, John had continued to work on the construction of the continuously pumped Heil tube he had designed at Woolwich to produce oscillations in the 10 centimetre wavelength region, and the prototype model now needed several kilowatts of electricity. As soon as they moved into their new accommodation, John had sent in a memo to the appropriate section at STC for a proper supply. Nothing happened, and even their mechanical vacuum pumps and diffusion pumps blew fuses before the main equipment had arrived. John told an assistant to put in heavier fuses, and wrote another memo. Still nothing happened, and in due course the electricity company fuse blew and they replaced that by a heavier one; this time John telephoned both STC headquarters and the electricity company. The latter said that they couldn't have blown the company fuse, and sent someone round to look at it. The fuse boxes were in a basement, and the company representative, who had gone down emanating scorn for these stupid scientists, came tearing up to say that the line from the street was running red hot, and, what bothered him still more, the meter, designed for lights only, had packed up and hadn't even recorded the electricity that had been used. Officials from the electricity company were inclined at first to blame John and he was relieved to be able to produce his copies of the memos he had sent. A new heavy-duty line and meter were installed in very creditable time.
Now that they had an adequate electricity supply, the work on the new valve based on the Heil tube progressed well. But once John's group thought they had a working model, they realised that there was no established way to test if it was working for the required wavelengths and frequencies. The tube was to be a receiver, but they knew that if it was supposed to receive at a given frequency, if fed energy it should give out radiation at the same frequency. However, they still needed a detector to demonstrate the presence of the resultant radiation. Then someone had the idea that if they could get their system to oscillate at all, the generated microwave energy should be quite simply detectable by a low power torch bulb fitted with an aerial of two short wires each measuring half the required wave-length.
To try out their detector, they darkened the room and moved the embellished torch bulb around at likely distances from the tube. They had had no luck with their first attempt when Mr Gibson turned up with a small inspection team from the Admiralty. John was pleased by the way the visitors appeared to understand both his explanation of the equipment and his hopes for his elementary system of detection of any microwave radiation. While he was elaborating on the techniques, John pulled down the blinds to show how he would move the torch bulb around in the dark exploring likely points. To his amazement, the bulb suddenly lit up. Calculating furiously in his head as to where would be the next areas to try, John kept up his patter and there and then proved that the right radiation was involved, for the bulb lit up and went out at every appropriate distance for 9 to 10 centimetre standing waves. Taking the apparatus apart later to ascertain the reason for his success, John found that a hole had been burnt in the anode creating some internal reflections that had increased the efficiency of the device.
Concern was being expressed in some circles that microwave radiation might cause brain damage. When John heard about this, he decided that it was unlikely, assuming that the microwaves were rapidly absorbed by water contained in the body, simply warming it up a little. He and his colleagues did find that they often had headaches at the end of a day using the equipment at high power, but their belief was that this was the effect of working eight hours or more in a warm, darkened room in their shirtsleeves with the windows shut.
The first heavy bombing raids started on the night of September 7th 1940, when John and Reinet were having a short cycling holiday. They came into the outskirts of Oxford, and booked a room in a small hotel where they left their bicycles and luggage before going out on the river. That evening, as people streamed out of London, all the hotels and guest houses in Oxford were rapidly filled, and many Londoners found no rooms available at all.
John and Reinet cycled home the next day, with no feeling of going into danger. They had their jobs to go to, and assumed that the probability of their flat being bombed was low. Once back in London, however, they did see the advantage of sleeping in the Bloomsbury Square trenches. With his usual practical foresight, John had already bought two lilos and two down sleeping bags, and in the evenings they would take them down to the far end of a long trench where no one would need to walk over them. Others were also kept away from the area they had chosen by the wet floor, from which the lilos afforded good protection. They both slept well right from the start, and were much annoyed by the air-raid Warden who would wake them at three in the morning to tell them the all-clear had gone. They soon had him trained to leave them alone, and they woke themselves with their own alarm clock in time for a wash and breakfast back at the flat before they went to work.As the evenings got darker, the bombing got earlier. One evening they were in the middle of a meal, entertaining themselves by judging how far away each bomb was by listening to the Doppler effect (only if the bomb scream moved up the scale was it approaching them) when they heard one that seemed fairly close. They both found themselves sitting on the passage floor cradling their plates without a word having been said. After that, Reinet would take the supper down to the trench, where John would join her on his return from work, very late, as he was now supposed to be at work from eight in the morning to seven in the evening six days a week. Between supper and retiring for the night, they would both read "Saint" stories, or catch up on reports to be done for work. John's journey from Eltham became extremely difficult at this time. Buses, trolley-buses and trams were all constantly re-routed round bombed streets, and passengers frequently had to ask a bus conductor where his bus was going and get on it if it seemed to be going in roughly the right direction. John noted that the eleven-hour day did not increase productivity all that much, for people became tired. Many staff took their newspapers to work to read them there, having no other time in which to read them and a barber had to be brought in to cut everyone's hair because all the barber's shops were closed outside the new working hours.
The STC houses at Eltham were eventually damaged when a house across the road was hit, and a lot of papers got sucked out into the road. The police were aware that secret work was in progress and, not daring to even look at the papers, blocked off that section of the road until the STC staff arrived to pick them up. This prompted STC to look for alternative premises, and in November 1940 the whole valve division moved to Ilminster in Somerset. The production section was re-established in an old rope factory, and the research and development sections took over the recently completed buildings of a new school.