R. C. Hanna, brother of Geoffrey Hanna 1945

My elder brother Geoffrey graduated in 1941 along with Brian. The two of them were awarded DSIR studentships to be taken up after the war. PhD's were to be few ! Next memory is of them sharing accommodation at ADRDE Malvern with another physicist, John Robson. What talent! Two went to Canada where John measured the half life of the neutron, Geoff, with Bruno Pontecorvo, set an upper limit to the mass of the (electron) neutrino and much more. Brian I knew again when I returned to Cambridge for a PhD. He acted as compere of the entertainments presented at the Cavendish Dinner. He urged the singers to relax."This is not Bach!" I remember a couplet from one song. "And when I've ceased contributing to knowledge “Then I can be the master of a Cambridge college". Untrue ! Considering the whole of the material presented, Professor Bragg took on the role of Queen Victoria.

Brian Pippard 1945

It was towards the end of the war, and an advertisement came out that Pembroke wanted to appoint some Stokes Students for research in physics; and John Ashmead (who was my superior in Malvern) suggested I should try for this. So I went in for it, and in due course I was invited for interview. There were five or six of us in the Master’s Lodge, waiting to be interviewed by the committee, which consisted of Prof. Bragg, and Prof. Todd, and Prof. Norrish, and the Master of Pembroke, and that sort of thing—pretty formidable. We were all chatting; and everyone else was so wonderfully clever, they’d all published papers in the Royal Society Proceedings—and they were sent for, and each had half an hour or so; and my turn came, and I think they took about ten minutes or quarter of an hour, and dismissed me. I’d published nothing, because of the war. So I was somewhat surprised when I found I’d been awarded one of the three studentships. I didn’t mind—I came back to Cambridge, rooms in college and all that sort of thing, and got to work. And it was about a year later, at a garden party, old Monty Butler the Master took me aside, and said that I ought to know they’d decided to put up the pay of the other two Stokes Students… But not mine. He said, ‘For one thing, they’re married, and you’re not—you’re living in college… And the other thing is… you weren’t really on our short list, but we did need someone to look after the Chapel music.’ [As Brian was fond of saying later: ‘If you’ve got it, flaunt it!’]

Robert W. Whitworth 1954

I can claim the privilege of being one of Brian's early research students even though when I last met him he knew me well but denied ever having been my supervisor. The story is that my project on liquid helium (not Brian's subject) was proposed by Donald Osborne. Donald got me started over a few weeks in the long vacation and then promptly left for East Anglia. Brian was appointed my supervisor, but after one year he went on sabbatical to the United States, and David Shoenberg took over. In those days one had to stand on one’s own feet, but I learnt a lot from Brian, most especially to concentrate on understanding a problem rather than just following the mathematics. I have done my best to emulate him in this respect, finding it both productive and very satisfying. I hope you have a very good meeting on 11th May.

David Llewelyn Williams 1957

I joined the Mond laboratory in 1957 with a First in Physics from the University College of North Wales. For the first two years I shared a research room with Brian, where, as a bumbling graduate student, I could observe his consummate experimental skill. His impressive manual dexterity when handling delicate specimens was perhaps a tribute to his musical training. His experiments were meticulously planned in advance so as to obtain as much information as possible and they always finished in time for him to leave for his college duties. He somehow tolerated my own inexperience and he certainly taught me how to plan experiments. He also revealed to me a way of thinking which I had not previously encountered. Suddenly a lot of Physics made more sense to me. His book, Classical Thermodynamics, published during my time there, has also influenced many of my students. In the summer of 1967, Brian was invited to lecture at the Simon Fraser Summer School held at the emerging resort of Whistler, British Columbia. He was joined by Charlotte and the three girls and I recall an idyllic time in fine weather. Brian played on the rather marginal piano at the Inn and his lectures were pretty good too! Subsequently Brian visited us on two further occasions; I recall a small dinner featuring a large salmon at our home and also a Chinese Banquet in his honour hosted by Simon Fraser. I like to think he enjoyed his time here in Vancouver and was pleased with my progress at U.B.C. I owe Brian a debt of gratitude, both for his forbearance with my shortcomings and for the enlightenment he provided which made my success possible. I am indeed privileged to have known him. John Waldram 1959

My first sight of Brian was in the newly instituted ‘Advanced Half-Subject’ in 1957. It was the first time that any form of ‘modern physics’ had been allowed into Part I, and Brian was scheduled to deliver a course on wave mechanics: I was one of his large excited audience. He certainly impressed me. In his trademark roll- necked sweater, he lectured entirely without notes—and without error—his voice light, his presentation elegant and illuminating, a little theatrical. The following year Joe Vinen sent me from Pembroke to Clare for supervisions with Brian, and for the first supervision he requested an essay on special relativity. We’d been subjected to an amusing but muddled course on it from Teddy Bullard, and I’d been forced back to the textbooks, where I discovered four-vectors. Rather pleased with myself, I prepared my essay in this new language, and handed it in ahead of time. When the day came, my partner Andrew Bennet and I climbed the stairs to Brian’s rooms, and discovered he shared the set with a theologian, Charlie Moule: in penetrating through the sitting room to Brian’s inner sanctum, we had to run the gauntlet of ten earnest dog-collared figures beavering away on the text of the New English Bible. We found Brian at a dimly-lit table, and sat down. Brian coughed, peered at me, held up my darling essay fastidiously by one corner and enquired tartly ‘What is this?’ before letting it flutter dismissively to the table. I came later to understand how deeply he mistrusted any abstract form of mathematical formalism: he knew only too well how students can wrap themselves in elegant equations, and fail to understand what they are doing. On this occasion he wasn’t content until he knew I could explain it all, as Einstein would have approved, by imagining myself travelling on a very fast train or riding along with a photon. Andrew meanwhile kept his mouth shut, and opened his eyes ever wider as my interrogation continued. Brian’s dislike of formalism went even further. The following summer, before I started research with him, he sent me off with half a dozen papers to read at home. As soon as I glanced at them, I realised I was in trouble: they were all concerned with the new BCS theory of superconductivity, and written in second quantisation, which I’d never seen before. Useful libraries were far away. All I could do was return to Cambridge several days early, hoping to make sense of it all, and deeply fearful of failing before I’d even begun. But to my uneasy surprise, Brian never mentioned those papers again, nor did we discuss BCS theory until my third year, when I had experimental results to analyse. Much later I came to understand. The fact was, Brian hadn’t learnt second quantisation either, and had no intention of doing so—just as he’d always refused to learn to drive —but he’d thought it useful to have someone around who had. During my first year he put me up to give a seminar on the recently discovered Giaevar tunnelling in superconductors, and seeing that my seminar came out full of creation operators, he must have concluded he’d achieved his objective. What I got from him, instead, was a master-class in experimental technique. I was extremely lucky. He’d just decided he should give up working at the bench (he was spending much time planning the new Magnet Lab), and handed over to me the apparatus he’d been working with. Its experimental design was a model of effective simplicity. For instance, the frequency of the klystron source had to be stable to one part in a million over periods of up to ten minutes, which Brian achieved, not with some elaborate feedback network, but using no more than draught protection, a micrometer tuner with weight and pulley to eliminate backlash, and a stack of carefully aged high-tension batteries as power supply. (These batteries were not without hazard, as they had very little internal resistance, and the stack voltage was 2000V. He warned me to wear rubber-soled shoes, and always to keep one hand in my pocket when connecting up the wander-plugs, so that the shock, if it came, would be unlikely to pass near my heart.) He taught me how to prepare the samples of tin–indium alloy, turning the slugs into wire using tallow and draw plate, and together we practised strain-annealing to make the wire into single crystals. He showed me how to electropolish my samples so that the surface was smooth to a fraction of the wavelength of light—and how, when mixing chemicals for the perchlorate polishing solution, to avoid taking it through the explosive region of its phase diagram. He showed me how to mount the shiny rods on the delicate fused-quartz frames he’d made himself. Best of all, after noticing that, without being told, I’d devised a sequence of observations that mitigated the effects of drift, he must have decided I could be trusted, and left me alone to get on with it. It was, of course, all before the days of personal calculators and data loggers: all readings had to be written down by hand on Mond data sheets, and calculations performed by slide rule. (The lab did own one large electro- mechanical calculator, but since it had an insulation fault and its keyboard tended to be live, it wasn’t popular.) When it came to writing papers, he wasn’t as hard on me as on some, but I do recall him murmuring in cautious and reflective mode, ‘I see you favour the split infinitive, John.’ There was also much very cheerful and well-lubricated entertainment of Mond students at Porson Road, greatly aided by Charlotte’s marvellous cooking. Usually there would be some music: Brian might oblige at the grand piano for a while, but we also descended sometimes to the banality of comb-and-paper or jew’s harp. As the years passed, I learnt a great deal of physics from Brian, too much to set out here, and we wrestled together over problems in superconductivity. We also had much contact over teaching, for I chaired the Teaching Committee for two periods during which he was closely involved in academic planning. He insisted on strong teaching when departmental appointments were to be made. There were battles royal during which he tried to exclude from the developing syllabus general relativity, the grand canonical ensemble, group theory, formal quantum theory— anything he felt dangerously formal—while the theoreticians hammered the table, insisting, and I did my best to hold the ring. Earlier, there was a hilarious period during the editing of Cavendish Problems, which he sent out to research students, working in pairs, to check, and to generate the numerical answers to be printed at the back. The trouble was, the students couldn’t agree, and were usually both wrong: Brian was forced to take it all back into his own hands. He and I pushed the boat out too far on Tripos reform: the Waldram–Pippard mark norms, intended to allow for the uneven distribution of talent between different subjects in Part I, were deeply resented by most other subjects, and quietly abandoned after three or four years. The teaching committee also allowed me to see Brian once in uncharacteristically unconfident mode. We had introduced student questionnaires, and not a few senior figures came to me, as committee chair, to discuss unflattering responses: it was instructive to see how sensitive most staff were to student criticism. To my amazement, there came a day when Brian himself got a poor response from the Part II class—Brian, whose lectures were normally such a tour de force. But he discussed it all with me extremely thoroughly, and plans were laid to correct the situation. There was one other occasion when he seemed vulnerable. He’d produced a new paper in superconductivity, and asked me to read it in draft. As so often with Brian, the new ideas were subtle, and took some absorbing, so it was perhaps a fortnight before I returned to say how interesting I’d found it. I then realised, from some small comment he made, that he’d been on tenterhooks for days lest I’d discovered some error in his maths. I was amazed: there was, of course, no error. Two final surprises. I didn’t realise until listening to his daughters at the memorial concert how enthusiastic an outdoor person he was, though I did remember him being towed behind a boat on Lake George, after the Colgate Conference in 1963, holding a board that allowed him to be drawn deep below the surface and return, depending on how he tilted it. Also, in helping Malcolm Longair prepare the usual Memoir for the Royal Society, I’ve realised how very tidy Brian left all his papers. It was obvious from them what a close and benign interest he took in the history of contemporary physics: he wrote an enormous number of memoirs, obituaries and book reviews that I was completely unaware of, and he also left personal accounts of his experiences that make fascinating and revealing reading; I’m only sorry I hadn’t seen them earlier, when we could have discussed them.

Andy Phillips 1961

I first came across Brian on Friday October 12th 1962 at 9.0am. He was giving for the first time the Lecture course on Forces and Particles, and for me it was the first physics lecture of my undergraduate career. I can’t remember anything about the content, but I can remember the warning that came at the beginning. The exact words are lost in the mists of time and the apprehension of that first lecture, but the gist of the warning was that physics is a difficult subject and that if we were not prepared for difficulty we should follow easier options (one of which was the alternative course given by John Baldwin, who was also my supervisor in Queens’). I have still not worked out why Brian felt he needed to warn us—was it reverse psychology or real concern?—but I do know that when I taxed him about it some years later he denied all knowledge. What was certainly true was that physics was much easier for him that for almost anyone else. In many cases Brian had a unique approach to problem solving that was much less straightforward to those who did not share his almost geometrical vision. This was perhaps most obvious in his book on Response and Stability, where I am still at a loss to know why I am acknowledged for help with the section on Broken Symmetry. Brian clearly derived more from our discussions that I thought I had contributed. In contrast, for me his most valuable book was Classical Thermodynamics, which was almost magical in the way in which a full scientific theory was constructed from almost nothing. Extremely clear, and above all concise, it let you understand the full structure of the subject almost at one sitting, although admittedly probably not at first acquaintance. It was a little galling in the early seventies, when developing a theory with colleagues at Stanford for the “anomalously” low thermal expansion of vitreous silica (it turned out it is not anomalous, but that the crystalline forms of silica have an extra contribution to the thermal expansion arising from the α-β phase transition) to find that Brian had already developed a model 15 years earlier for this phase transition that allowed us to derive the results we needed. Thinking back, it is surprising how different it was being a research student with Brian than it is for current research students. Instead of becoming part of a research group working with established equipment, I was essentially given a desk and a copy of Brian’s most recent paper on ultrasonic attenuation in superconductors. It was much the same for everybody else, and we were all expected to design our own cryostats for manufacture in the workshop. The only common element was liquid helium jealously guarded to the last drop by Frank Sadler. We felt we had won a major battle when we were finally allowed to take a helium Dewar to the cryostat instead of taking a cryostat to the liquefier. Still, it was all good training: soldering cans to be Helium 3 tight and rewiring all the equipment was ideal preparation for installing plumbing and rewiring houses in later life. Brain had a well established routine as part of his role as a supervisor. He always dropped in to see what you were doing on his way out of the Department at about 6 pm. This fitted in very well with opening time at the Eagle, and meant that he was always available to ask and answer questions. However, he also dropped in to the labs on his way into the Department, and it was very irritating to arrive for coffee after an all-night session obtaining results to be presented with a full explanation of what you had found. We soon made sure that all the results and graphs were well hidden before we left after an all-night run. Brian was an inveterate fiddler. If there was anything lying around that was at all unusual he always picked it up and played with it. At least he did until one memorable occasion when he started to play with an automatic centre punch, the sort that punches a hole when pressed. After a few minutes he obviously unscrewed something that wasn’t meant to be unscrewed, and the whole thing flew apart, ending up in the four corners of the room. Brian suddenly remembered an urgent appointment. Perhaps the most vivid and traumatic memory was the time he went through the first paper I wrote. Like many scientists, I suppose for me one of the attractions of doing science at school and university was that you didn’t have to waste time writing silly essays. What Brian did was to go though what I had written paragraph by paragraph, sentence by sentence and word by word. What does “this” refer to, why is this verb singular and not plural, what is the logic of starting a new paragraph here, what on earth does this sentence mean? I think it took two hours one day and two the next, but I learnt a lesson that I have never forgotten about clear scientific (or indeed any other) writing, and the importance of being clear, logical, concise and precise. When I complained mildly at the end Brian’s comment was “If you think I am fussy, you should try David Schoenberg”. Since my time as a research student I have met and worked with many good physicists, and it took me some time to realise just how many different styles there are, and how each can be successful in their own way. Brian was a master of the intuitive approach, without reliance on mathematical formalism, but with a delight in geometrical solutions (which to many of us were more baffling than formalism). To his research students he demonstrated an approach that is a model of how to tackle new problems, and his guidance will always be remembered.

Gordon Donaldson 1962

Looking through my 'drafts' folder I realise that I neglected to send you a message with apologies for my absence from the ABP festivities. The reason is, curiously, a previous engagement with a distant connection to the Mond. I am booked to attend a dinner in St Andrews to celebrate the 90th birthday of David Finlayson, who was Jack Allen's first hiring when he moved north from Cambridge (1947?). So all the best for a memorable weekend, and best wishes to all my colleagues of nearly 50 years—superconductivity has been very good to us, thanks in large part to Brian. Kind regards to you all, Gordon

John Payne 1966: Brian as administrator and laboratory designer

I missed Brian’s lectures on Thermodynamics because he was on leave during my final undergraduate year reading for the Natural Sciences Tripos in Cambridge (1955 to 1956). Ten years later, I was recruited from industry to assist the Secretary of the Department of Physics, Ian Nicol. There I met Brian, who was Deputy Head of the Department. He had an impish sense of humour. One day in 1966, we were talking informally to the architects who were to design this building (the “new” Cavendish Laboratory). Brian made a somewhat startling statement. It was about the importance of …bureaucracy! Why? He was on the University’s General Board, where he was promoting devolution of decision-making; he had been influential in persuading the University not to build a tower block for Physics in the centre of Cambridge but to develop the West Cambridge site for the long-term expansion of the physical sciences; he had helped choose the site architects and had made sure that the Department were able to brief them directly on a new building for Physics; he had advised government on the design of new science laboratories in universities, and he was in the process of founding Clare Hall. He had good cause to be thinking about administration and its handmaid, bureaucracy. When the General Board decided to devolve some of its duties, Ian Nicol took all thirteen existing departments of the Physical Sciences under his wing. In 1966, Ian left the Cavendish to become the first full-time administrator of the School of the Physical Sciences. He later became Secretary General of the Faculties. His recent “Times” obituary states: “It is clear that, without his tact and willingness to make himself known and trusted by the departments concerned, the school would not have developed successfully.” Here, I think, was the sort of person whom Brian saw as vital to a good bureaucracy. Coming from industry to the Cavendish, I felt my good fortune immediately. I was given the job, among others, of link-man between the Department and the architects, Robert Matthew, Johnson-Marshall and Partners. Brian wrote later that the architects were “chosen for their notable work in the planning of York University.” Their site plan for West Cambridge envisaged well- separated buildings in a parkland landscape. Funding was from the government. Any private funds raised would be subtracted (a rule long-since abolished). The norms were tight, to say the least. The building’s cost turned out roughly the same as that of a good quality dwelling house of the time. I cannot believe that its carbon footprint would be considered up to scratch now. When the architects finally waved goodbye to us, they mentioned, in passing, that we would need to renew the roof every five years or so. Brian recounted later that hesitations, delays and parsimony in the granting of government funds were a blessing in disguise. He wrote (I quote) “they allowed time for a much more searching examination by the architects of the Department’s stated requests than might normally have been expected.” The Department was forced to examine its assumptions and consider more carefully the effect of the building on the Laboratory’s social organisation, especially the balance between privacy and interaction with others. For their part, the architects received a detailed and well thought-out set of needs from the Departmental Building Committee, led forcefully by Brian. A supremely important requirement, in his view, was the ability to modify the building easily, in order to meet new research needs as they arose in future. Another was the need to minimise interference from vibration, whence his desire to avoid a tower block. Devolution and consensus were, I think, intrinsic to Brian’s experience of the Cavendish under the headships of Lawrence Bragg and Neville Mott. I believe that these attributes sprang naturally from what I can only call the “Cavendish spirit.” It had enabled the Department to adapt to huge changes in the practice of scientific research. In the early 20th century, an American visitor gave some impressions of the Laboratory, under J.J.Thomson. He wrote: “It is obviously dominated by the personality of J.J. and yet I have never seen a lab in which there seemed so much independence and so little restraint on the man with ideas.” J.J., that great designer of experiments, was by all accounts clumsy with the apparatus, depending heavily on Everett, his personal assistant. Brian, in contrast, was a deft experimentalist, yet very conscious of our continued dependence on the assistant staff. We certainly relied on them greatly to help get the details right in the building’s design, and even more so when executing a complex series of moves to our new quarters, between 1972 and 1974. Brian’s vision of consensual government depended on trust and effective devolution, both dependent, I believe, upon a mutually held moral outlook. Years later, he published a paper in the Cambridge Review, entitled “The University as a Model of Consensual Government.” As I recall it, he expressed the hope that the model might spread into our national political life. To reach a consensus requires parleying, haggling and horse-trading. A residual intellectual dispute might need to be resolved. Brian relished that. In the early 1980s, when he had become Head of Department, and I had moved on to serve the Physical Sciences as a whole, I would occasionally witness the irresistible force of Brian’s ideas meeting the immovable object of someone else’s views. For the quiet bureaucrat, this was a delightful spectator sport. If he did suffer defeat (unusual), he did not mope. There was too much else to engage his curiosity. Finally, here’s a tale I hope you will enjoy. It is from our early days in the Mott Building of the new Laboratory. Its top floor consists of offices and seminar rooms. The internal rooms were heated and ventilated by air, which entered through grilles in the ceiling and was extracted, by way of the corridors, through grilles in the doors. The new occupants felt these rooms to be stuffy. Experts were called in. Measurements were made...the rate of air change was more than adequate. Heads were scratched...no solution was offered. The client was being unreasonable.

Brian became aware of the problem. One day, he took me off to the stores, and requested a bottle of hydrochloric acid, and another of ammonia solution. Up we went to one of the offending rooms. He unstoppered the bottles, and held them up, mouths close together, near the air inlet. A white cloud of ammonium chloride appeared and followed the flow of air. It crossed the room, clinging tightly to the ceiling, flowed down close to the wall and out through the exit grille. At Brian’s suggestion, simple flanges were made, in-house, and fitted beside the inlet grilles. The flow was broken and the trick was done. A practical man with a questing and formidable intellect, Brian did not disdain apparently simple problems. He was appreciative of his bureaucrats, being kind by nature to those whose job it was to serve. In recent years, I saw him regularly at various concerts in Cambridge. An accomplished musician himself, he always had a penetrating and illuminating comment to make on what we had heard. He was a great and a good man, with a special sense of humour.

Laurie Haseler 1969

You may be interested to learn that, nearly 40 years after having first heard his name, I actually met Ernst Sondheimer a fortnight ago. We met in Croatia, and in fact spent a week together there. We were on a trip organized by a company called NatureTrek, in a group of about a dozen, in Dalmatia, with a specialist botanist and ornithologist as leaders. Ernst is quite knowledgeable about alpine plants, and has been a significant alpinist, which may explain why he is so active and full of life at 85. My wife Jan is into butterflies and moths, and their food plants, hence the botany, so we often go on this sort of holiday. I had seen Ernst’s name on the list of people on the holiday. You can imagine his face, when I said, are you Ernst Sondheimer, as in Reuter and Sondheimer. He had lots of interesting things to say about Cambridge just after the war. I learned that Ernst formulated the equations but could not solve them, then he heard from Harry Reuter, at Manchester, who offered to use his knowledge of Wiener-Hopf integrals to solve them, and then Ernst spent the long hot summer of 1947 evaluating the solutions. I also leaned that Harry Reuter was the son of Ernst Reuter, the Burgermeister of Berlin, during the Berlin airlift. Maybe you are familiar with all that. I don’t think I’d heard it before – of if I had, I’d forgotten. It’s a long time since I’ve thought about electrons in metals. Ernst also told me about the memorial events for Brian Pippard next Sunday and Monday. I’m trying to work out whether I can come.

Thorsteinn I. Sigfusson 1978

Dear John, I have just returned from a trip in Europe - great to hear from you! I was indeed considering to come to Cambridge - but now our Minister of Industry is planning a meeting in Oslo on Monday and Tuesday and I have to be there. I would like to ask you, dear John, if you have the opportunity, to convey greetings from me here in Iceland. Actually we were considering to name our first born (Cambridge Maternity Hospital April 16 1980) Brian—but ended by the name David—both names related to the LTP area of the Cavendish!!! David Thor is currently a medical doctor at the University Hospital in Iceland. Our second child Dagrun Inga is in the Medical School of the University of Iceland (born in 1988). Our third and youngest child is Thorkell Viktor who is eagerly awaiting his driver’s licence these days! With all the best regards, Thorsteinn I. Sigfusson

David Khmelnitskii – suggestions for Russian invitees:

Dear John, dear Peter, After giving to this matter some thoughts, I came up with several suggestions. Name of Brian Pippard was enormously popular in the former Soviet Union because of the following contributions:

1. Anomalous skin-effect, first of all 2. Non-local diamagnetic response of superconductors and correlation length. The words "London's case" and "Pippard's case" were a common slogan in Soviet union. 3. Geometric resonance in sound attenuation. 4. Shoenberg magnetism, named this way by Pippard.

The most important development along direction 1 was prediction by Azbel and Kaner the cyclotron resonance and discovery of anomalous penetration of high frequency field through thick plates of metals in parallel magnetic field. There are very few survivals of this revolution. The best speaker, to my view, is V.F.Gantmakher, discoverer of Radio-frequency size effect. Prof Gantmakher is, in many respect, Pippard in USSR, an experimentalist, who is at home with theory. He keeps a religious admiration to Brian and his memory and, as much as I know, Brian felt high admiration to him. My third suggestion is A.F.Andreev of Andreev reflection at NS boundary. He is linked to Pippard through Brian's study of NS boundaries. Yours, David