After his return from Russia, John still had a programme of work to complete using his existing ion source and, despite his disappointment over the grant application, he continued with that. He was also invited to write an article on heavy ions for a book on nuclear reactions (published in 1959), which kept him busy in the evenings. At the same time he was working on his DSc thesis (a collection of his published papers with an extra written piece linking them), which he presented successfully in 1957. It was not in his nature to complain about things that upset him and although he told Reinet that he had been refused permission to apply for a grant, he did not explain how much this meant to him. Seeing him keeping busy, it was not immediately obvious to her that the basis of both his work and his self-esteem was in jeopardy, his usual optimism having deserted him. For some time he became more and more depressed until one day David asked him why he was so down. Reinet was startled by the question, for she had genuinely not noticed John's condition, but before she had time to recover from her shock, John had launched into an account of his problems. As is so often the case, talking about his situation made him feel considerably better, although for John, this could only happen after someone had expressed an interest. When ill, he often acted in the same way: he far preferred someone to notice that he looked unwell than to announce the fact himself. Once it was confirmed that he was ill, he would take to his bed and quietly entertain himself with games of patience until he was better.
The impasse did not in the end last for very long. One day John was telephoned by Dr Leslie Hardwick, a lecturer at the Dental School, who wanted to know if it was possible for the Physics Department to make a radioactive isotope of fluorine for him to use in some research he was doing. John quickly decided that the radioactive fluorine-18 would result from adding a proton and a neutron to oxygen-16 and that this could be done by bombarding oxygen-16 (as found in distilled water) with helium-3. The next morning John got this going, and soon was able to ring Dr Hardwick to tell him that there was a solution containing fluorine-18 waiting for him, and that he should collect it quickly as the isotope had a half life of only 110 minutes and would remain radioactive for a limited time only. Dr Hardwick then asked if there wasn't such a thing as a Geiger counter for measuring radioactivity and John agreed that indeed there was, realising immediately from the question that the dentist did not have much idea of how to use his radioactive fluorine. So he suggested that Dr Hardwick come over to the Physics Department and use the Geiger counter originally bought for the final year students. They arranged a date, and Dr Hardwick arrived carrying some extracted molars.
Dr Hardwick told John that there was a lot of clinical evidence that fluoride ions-1- in drinking water protect teeth from decay. Areas where the water contained fluoride naturally had been compared with areas where it was not, and less dental decay had been found in the fluoridated areas. Some drinking supplies in the United States had also been artificially fluoridated more than ten years earlier and comparisons between the rates of decay before and after fluoridation had shown that it protected teeth, although it was noticed that the protection was greater for people who had grown up with fluoride in their drinking water. However, a very small amount of fluoride in the water, around one part per million, seemed to be quite adequate and Dr Hardwick had decided to try and investigate the mechanisms by which it worked. He was not the first to try to do this, and it was hearing of work in the United States using radioactive fluorine that had made him want to try this method.
Looking at the literature, John found that three theories had been put forward to explain the beneficial effects of drinking water containing fluoride. The most popular theory, and the one Dr Hardwick was hoping to prove, was that the chemical formation of fluorapatite from hydroxyapatite in the enamel makes it less soluble in the dilute acids that are produced by bacterial action on sugar in the mouth. The second theory was that the fluoride itself inhibited bacterial activity and the third was that fluorine was essential in the initial formation of teeth.
The experiments quickly showed results. John and Dr Hardwick put a tooth into a solution containing one part per million of fluoride from ordinary sodium fluoride with a little added fluorine-18. The tooth became radioactive in seconds and washing it under the tap reduced the radioactivity only a little, satisfying them that teeth could absorb fluoride ions from drinking water. But so far, this only repeated work that had already been done, and John realised that it did not go very far towards an explanation of the effects of fluoridation when he calculated that if teeth continued to take up fluoride ions as fast as they had done in their experiments, teeth in fluoridated areas would become one hundred per cent fluorine in a year or so.
Their next experiment was to test the effects of acid on teeth that had already taken up fluorine-18. Bathing the teeth in water reduced the activity only slowly, but using an acid solution brought the radioactivity down very quickly suggesting that the fluoride ions were released by the acid. This did not completely disprove the theory that fluoride was making enamel harder by a chemical reaction, but it did tend to indicate that something else might be going on.
Then they tried passing teeth through a series of solutions with different proportions of fluorine-18 and its non-radioactive version, fluorine-19. Teeth made radioactive by a first pass through a solution containing fluorine-18 lost their radioactivity when put into the non-radioactive fluoride solution more quickly than they did in distilled water, only to become quickly radioactive again when exposed to a further solution containing fluorine-18. This could only mean that there was an exchange of fluoride ions between the teeth and the surrounding solution, which indicated that while teeth could take up fluoride ions, these were not fixed chemically in place and could just as easily be lost again. John began to think that there must be a number of sites, in the crystal structure of each tooth, capable of holding fluoride ions but also able to release them. John's conclusion, after several further experiments, was that the teeth of people who had drunk fluoridated water from birth had more sites capable of taking up fluoride ions and these sites were constantly recharged whenever fluoridated water was drunk. In acid conditions, such as times of bacterial attack, highly reactive fluoride ions were released into the plaque on the surface of the teeth in sufficiently high quantities to suppress bacterial activity.
The experiments that produced these conclusions were done fairly quickly, but John continued to work on teeth using radioactive tracer techniques for several years, further work on fluoride uptake by plaque being done by Dr J N Kudahl. John was promoted to Reader in Physics in 1958 and Dr Hardwick took up a professorship at Manchester University but they continued to liaise over some of their experiments and they published several joint papers on their results. Having seen the results of studies of rates of tooth decay in fluoridated and non-fluoridated areas and having also demonstrated to himself a clear mechanism as to why this should be so, John threw himself into converting non-believers with some passion. He wrote letters to newspapers and gave public lectures, particularly in districts where there were ongoing debates about future fluoridation of water supplies. But in spite of his firm belief that fluoridation of all water supplies that did not have a natural content would improve the dental health of the whole nation, he still felt that it would be reasonable for individuals to have a choice if they had some positive objection. With this in mind, he went to work on a device to remove fluoride from water within the home. After success in removing fluoride from water by running it over crushed bone (from a family Sunday lamb joint), he sanitised the procedure by using garden bone meal, which he calcined (heated to seven hundred degrees Celsius), and put into an ordinary domestic water softener in place of its resin and found that this worked very well. Details of his invention were published in the British Dental Journal.
At one point he turned his attention to producing thin sections of teeth. The thinnest sections available at the time were about twenty to fifty micrometres-2- thick, and were prepared by first cutting sections one millimetre thick and then grinding and polishing the surfaces. The fine grinding was done by rubbing sections over a powder of fine carborundum and diamond on plate glass with the end of a finger. Unfortunately, dental enamel is brittle and breakages limited the final result, so the head of the Bristol Dental Department offered one hundred pounds to anyone who could find how to reduce the thickness to five micrometres. The method that John developed in response to this challenge started in the same way, but once the section was approaching a dangerous thinness, he would cement it to a glass microscope slide using a contact adhesive and then carry on polishing the unattached face without any danger of bending or cracking, getting the thickness down to the required five micrometres. The polishing was time-consuming and he did a lot of it sitting in his armchair at home in the evenings. The section could then be studied under the microscope, still on its slide. Writing the work up, John did suggest that the section could be removed from the slide by soaking in water for a few hours, but warned that it might then be difficult to find.
In 1958, John gave a lecture entitled "The Importance of Being Bigger than a Beetle" to a group at a Birmingham school. Little was he to know how many times he was going to repeat it when he first assembled all the physics he could think of relating to animal size into an entertaining presentation. What he did was to postulate a human being that had shrunk down to the size of an insect and then work through the physical problems this creature would have one at a time. For example, such a tiny human would have a much greater surface area to weight ratio. Then a porous, human-type skin would make it evaporate water at such a rate that it would have to drink the equivalent of two to four thousand pints of water a day. If it were also warm-blooded it would lose heat so quickly that it would need to eat a colossal amount. A light and tiny creature would blow away easily. To these and to half a dozen other problems, he proposed simple solutions such as a waterproof skin, cold blood and hooked feet. He finished triumphantly by pointing out that a person as small as a beetle would be a beetle. This talk became hugely popular, particularly with school science societies and John thoroughly enjoyed giving it. Aware that some science teachers might think the subject too frivolous, he had an alternative title for what was essentially the same talk: "Qualitative Effects of Change of Scale".
At about the same time John heard of an organisation whose aim was to ban all nuclear weapons - the Campaign for Nuclear Disarmament (CND) and he joined it immediately. Soon he was deeply involved with the movement. He joined in the Aldermaston marches that took place each Easter for some years and was an active supporter at meetings, often as a speaker. Only a year after joining, he made a six-day tour of Yorkshire with J B Priestley and Jacquetta Hawkes, the three of them holding meetings in support of CND wherever they went. As was now usual with John when he believed strongly in anything, he used letters and articles to argue his case as well as public meetings. Professor Moon, who had disliked John's socialist leanings, also disliked his connection with CND and objected to John giving his address as Birmingham University Physics Department in any of his letters or articles. While John might also have rejected the use of the status of his position at the University to influence people he felt that his qualifications as a physicist, and a nuclear physicist at that, lent weight to his opinions, but he did try to avoid implying that he was stating any view for the whole department. In 1961 he collaborated with Dr Simon Sevitt, a Consultant Pathologist specialising in burns, to submit a memo to Birmingham City Council explaining the effects of a nuclear device dropped on the city. John and Dr Sevitt used the first few paragraphs of the memo to say that they had become concerned that to spend locally collected rates-3- on Civil Defence was not only a waste of money, but also misleading to the general public who might think that the organisation could increase their safety. They then described in detail the effects of one ten megaton bomb dropped on or near Birmingham: from the centre of the explosion to five miles out, the area would be impassable for some weeks, and even eleven miles from the explosion there would be a lot of serious injuries. The fallout area would be quite unpredictable, its cigar-shaped shadow covering an area determined by current wind conditions. Sixty such bombs over Britain could extinguish all life. Their conclusion was that the same money would be far more useful in training adults and children to deal with peacetime disasters and in home accident prevention. These calculations made their mark on me, and I lost quite a lot of sleep waiting for the sirens to signal the approach of the first bombers or rockets carrying their deadly payloads!
John had no trouble persuading the rest of the family to join the CND and from 1961 to 1963, Reinet, Jane and I, together with David when he was available, all joined him on the Aldermaston marches. The route from Aldermaston to Trafalgar Square was over fifty miles to be walked in four days over the Easter holiday, the longest day being a gruelling twenty-two miles. John made sure that Jane and I were fit to do this by taking us out for walks on Sunday afternoons for some months beforehand increasing the distance by half a mile or a mile each week. Reinet's work as a teacher was taking all of her time and energy and she did not feel able to find the time for so much practice but she was still able to join in because the Aldermaston marches generated a pressing need for baggage handlers, caterers and organisers. For three nights the marchers dispersed to a number of schools and halls where they picked up their luggage delivered by lorries during the day and then each staked a claim to a small area of floor. Somehow the organisers managed to make sure all the bags arrived at the same place as their owners and that we all got a substantial evening meal and breakfast. John believed strongly in the efficacy of peaceful protests of this kind: he was convinced that the function of the marches was to rouse the interest of people who read about them in newspapers or saw them on television so that perhaps afterwards they would listen to arguments about nuclear disarmament. He did not want to bulldoze anyone into taking on his beliefs, but he did want everyone to have the chance to observe all the relevant facts in the hope that knowledge would point them to a sensible solution. So later on, when some members thought that not enough was being achieved and formed splinter groups such as the Committee of One Hundred, which favoured a more confrontational form of protest, he tended to feel rather unhappy about the way things were going and lent less active support.
He used one of the later Aldermaston marches as a stepping-stone for a further trial of stamina. A week or so after the end of the march, while our training should still stand us in good stead, he suggested that he and I try to walk to Worcester along the canal from Birmingham, a distance of about thirty miles. Almost the whole route was along the towpath, absolutely ideal for a long walk as it avoided hills and was softer than tarmacadamed roads, but there were one or two places where we were diverted by ill-kept parts of the towpath or by tunnels and had to map-read our way to the next part of the path. John insisted on increasingly frequent breaks for food and attention to my blisters, and towards the end we were stopping for five minutes after every mile, but at last we got to Worcester. Disappointingly, a careful measurement of the route on the map showed the total distance to have been only twenty-nine miles but we were both pleased at our achievement. We finished the day by polishing off a Chinese meal in Worcester before catching a bus home.
By 1960 the cyclotron was going some way to earning its own keep by producing saleable radioisotopes. A frequent customer was a company that needed sodium-22. The technique for making this required the cyclotron to be taken off other work and then used continuously for two or three days and nights. Since it was undesirable for the technician running the machine to be alone, John and a small group of cyclotron users formed a regular rota to keep him company overnight, making cups of tea and, if possible, sleeping on a lilo in the control room. They were sometimes entertained by the laboratory mice coming out to look for sandwich crumbs and running apparently effortlessly up and down vertical single-core cables. At the end of the bombardment, someone had to reach round a lead shield to scrape the highly radioactive sodium-22 off the target and then put it in a lead pot for transport to the company, a job John usually did himself to prevent the technicians adding to their annual doses of radioactivity. (John's gamma detecting badge told him that he had absorbed eleven rems-4- in ten years, the permitted annual dose being one rem per year; the technicians also ran fairly close to the permitted limit.)
Relations with the company didn't always go smoothly; several times after a delivery, they said that they would not be wanting any more, and then later on would ask for some at short notice. John tried going to visit them to try and persuade them to make more regular orders, but the pattern remained the same. Eventually John took the initiative and used eight hundred pounds of some unallocated grant money to continue the bombardment at the end of one of the runs to produce a spare batch.
The next time someone from the company rang up, he clearly expected to hear the familiar moans about changing the cyclotron over and working nights, but instead John asked when it was wanted. The voice on the telephone said: "When can you do it by?" to which John was delighted to reply: "Will Monday do?" This little bit of foresight earned two thousand pounds that John paid into his research project funds in a type of creative accounting that was to become an occasional habit of his (causing more headaches for the management). From that time on, John always kept a spare batch of sodium-22 ready, and he was never caught out - it was always required in the end.
Travel became an increasingly important part of John's life, and something he always enjoyed. He had several trips to Saclay in France where there was already a cyclotron much the same size as the Birmingham one, but where some help was needed to make the synchrocylotron work. When in France, John always noticed the lack of the morning coffee break that in England was usually used to discuss some problem in a leisurely fashion and he was quite sure that the French habit of working straight through from eight until two was less productive. Later he also went to Yugoslavia to help with another cyclotron. There was a trip to Germany in August 1960 to join a German Peace Council conference and another trip to Germany for a heavy ion conference.
In August 1961, while Reinet took me and Jane to South Africa to visit her father (Gladys had died the previous year), he went to Japan. This was to join the seventh world conference held on the anniversary of the Hiroshima atomic bomb: John was one of the two delegates from Great Britain. To increase the number of speakers to an absolute maximum, the time allowed for each report was very short. John was required to give several of these brief reports and he used them to discuss the points of importance to him at the time. One of these was his distrust of the claim that the British government was keeping nuclear weapons as a deterrent. He asked his audience to imagine an accidental attack on a British base. While Thor rockets on these bases took fifteen minutes to fire, the warning of an approaching attacking weapon could be no more than half that. Therefore, he said, these weapons could only be of any use if they were fired first and therefore could act only as a provocation, not as a deterrent. In another report, he said that the horror of what was done to Hiroshima had affected the consciences of many western scientists and went on to say that the plutonium used for bombs could produce ten million kilowatts of heat for twenty years and the scientists released from building bombs could research methods of achieving this. He found reports from delegates who described the actual events when the bomb was dropped and the subsequent suffering of affected people rather harrowing. When the meetings were over for the day, delegates were given the opportunity to be taken to see the park now laid over the part of Hiroshima that had been destroyed or to visit leukaemia patients in one of the hospitals. During spare time, John hunted for souvenirs and eventually chose a limited edition print of an eastern Jay, and a set of delicately etched tumblers with a matching water jug. Dissatisfied with the shop's proposals for packing these for transport to England, he went back to his hotel and fetched a pair of pyjamas to help surround the glassware, slightly easing the strain on his own luggage.
The children's education was progressing satisfactorily. David won a scholarship to John's old college at Cambridge to read chemistry. At the last moment, David changed his mind and asked Trinity College if he could change to mathematics, and as he had obtained 100% in his mathematics paper, he was allowed to do so. John was mystified because he felt that pure mathematics niggled on about things that did not really matter, and he had been hopeful that David would want to apply his first class brain to science. Both Jane and I won places at Grammar schools. Jane went to the sister school to David's and so she replaced her brother as John's walking companion when he went to work in the morning on those days when he did not cycle. The conversations John and David had had on these walks were not to be repeated as Jane and John still lacked mutual interests. Jane's main memory of these walks was that John tended to walk a lot faster than her eleven-year-old legs found comfortable! When eventually Jane did begin to take an interest in party politics, she was inclined to follow the Conservative line, and John, who equated non-socialism with an inability to care, interpreted this as a lack of sensitivity. If Jane did make a caring remark, he reacted with some surprise.
More and more people were getting their own cars, and by 1960 most of John's friends had them. John noticed the problems these people had with their cars: in order to be able to afford them, they either went without holidays, or lived in inexpensive houses well out of town; they spent a lot of time or a lot of money maintaining them and John liked to say that he had no intention of spending his Saturday afternoons under a car. But by 1963, the family was much better off than it had ever been. John had also heard that it became progressively more difficult to learn to drive after the age of fifty, and, as that age had now crept up on him, he decided that he really ought to get on with some lessons. Characteristically, he planned out his own unique strategy and put it into action. He reasoned that when learning to drive, plenty of practice was necessary, but also friends might not be too happy to give a novice practice in their own shiny vehicles, and therefore he should first buy his own. He felt that he would get a more reliable car by starting off with a brand new one and having it regularly serviced. So, after surveying the market, he bought a Triumph Herald on the grounds that it had one of the smallest turning circles available together with sensible rubber bumpers, booked himself a course of twelve lessons and inveigled various University friends to sit with him while he practised. His preparations paid off, and he passed his test first time.
He did not allow the car to stop him exercising, preferring to walk or cycle to the University on ordinary working days, but he did find it extraordinarily useful in getting to meetings and to places where he might hunt for rare wild flowers and increasingly combined the two activities, looking up what plants were to be found near the location of a meeting in advance. He remained adamant about not spending time maintaining it: he taught me to do the regular oil, water and tyre checks and took it in to a garage for all other servicing. The family all took driving lessons and John gave hours of his time sitting in with each one of us as we practised.
Other ways of spending money never appealed to John: he didn't take to drinking, for example, and from the time when his cider-and-skittles days came to an end when he left Ilminster he was practically teetotal. He made no particular effort to avoid all alcohol if it came in a package with something else, and could eat a sherry trifle with as much enjoyment as anyone, but he could see no point in spending money on drink and preferred his head to stay clear. Once he could afford it, however, he took great pleasure in buying Reinet a bottle of sherry from time to time because he knew she enjoyed it. Neither John nor Reinet believed that alcohol was necessary for entertaining guests, and they evolved their own style of coffee evening where between two and six people were invited, usually colleagues or a selection of John's students. Dishes of sweets and nuts were placed round the room to be within everyone's reach, and freshly made coffee was handed round at intervals. The conversation was meant to be intellectual, about current news, politics and science and the method of selection of guests meant that there was little deviation from this rule. John and Reinet liked to think that art or music could also be discussed but if the references became obscure, Reinet would sigh heavily, say she wished she knew more about the subject and introduce a different one. This is not to say that they were not prepared to learn anything from their visitors. In particular, they enjoyed hearing from foreign students about the customs in other parts of the world, and would go to some trouble to encourage visitors who seemed shy to talk about themselves.