David Warner died on 9 June 2005 leaving a gaping hole in the lives of his family, friends and colleagues and in the nuclear physics community world-wide. A warm, friendly and helpful man, he will be sorely missed, not just by all the individuals close to him but in his role as a nuclear physicist. Dave, as he was generally known, was born in Philadelphia, and lived in the USA until he moved with his mother to Bournemouth in England at the tender age of seven. He was a national of both the UK and the USA and embodied many of the best characteristics of the citizens of both countries.

On leaving school he moved to the University of East Anglia where he graduated with a 1st Class Honours degree in physics. His graduate studies on nuclear orientation applied to experimental nuclear physics were undertaken at Sussex University under the supervision of the late Dennis Hamilton. It was here that he began to lay the foundations of his knowledge of nuclear physics, no doubt influenced by the presence in the Sussex physics department at that time of Professor J P Elliott and his theoretical colleagues. Given this starting point, it should be no surprise to us that he had an excellent knowledge and understanding of the theories of nuclear structure. It was easy to understand why many people asked if he was a theorist or an experimenter. He did not see it as a very meaningful question himself and was in no doubt about the fact that he was an experimenter. It did not stop him making many meaningful contributions to our understanding of nuclear models.
Following his PhD, he took up a position at Institut Laue-Langevin, Grenoble, in 1975 at a time when the reactor centre there was the world-wide focus of nuclear structure studies with slow-neutron-induced reactions. Simultaneously Arima and Iachello introduced the idea of dynamical symmetries into nuclear physics in the form of the Interacting Boson Model (IBM).
In collaboration with Hans Boerner, Klaus Schreckenbach, Walter Davidson and others, he exploited to great advantage the high resolution and sensitivity of the curved-crystal gamma-ray and double-focusing beta spectrometers, with their in-pile targets. He was quick to see the potential of the IBM to give a convincing explanation of the regularities in nuclear structure that their experiments were turning up. It was at ILL that he encountered Rick Casten, then at Brookhaven National Laboratory. This was the start of a long-standing and highly fruitful collaboration. Casten enticed him to Brookhaven and, much to his surprise, the move to the USA did not even mean much in the way of bureaucracy. Unknown to him, US law had changed and his application for a visa was met with the query 'Why are you asking for a visa? You are an American citizen.'
Dave's stay at Brookhaven from 1979 to 1986 was extremely productive in terms of physics and very happy in family terms with the arrival of daughter Jenny and son Steven. To some extent the family seemed to enjoy what one might see as an extended holiday, an atmosphere they recreated on later return visits, first to Brookhaven and later to Yale when Casten moved there. At work he and Casten were excellent foils for each other. Casten is well known for his translation of theoretical ideas into the kind of pictures that other physicists can understand. Dave kept their feet on the ground and together they turned the abstract algebra of the IBM into a readily understood and easily used tool for interpreting
the results of nuclear spectroscopy. At the same time, he continued to exploit slow neutrons as an experimental tool but now at the Brookhaven High Flux Beam Reactor.
Proofs of the existence of some of the dynamical symmetries predicted by the IBM, of the applicability of the model to deformed nuclei and some of the earliest evidence for
Bose–Fermi symmetries in nuclei flowed from their efforts. Dave's theoretical acumen was also demonstrated by their development of the revised approach to the IBM, called the Consistent Q formalism, which has now become the standard approach to IBM calculations. My own collaboration with him had started at ILL and continued at Brookhaven with joint supervision of Alison Bruce, a Manchester student studying neutron capture at the HFBR. He remained in loco parentis for both Alison and her contemporary as a student at Brookhaven, Ani Aprahamian. How much of his advice rubbed off is hard to tell but I know they both feel he helped and encouraged them to fulfil their potential.
Meanwhile nuclear physics in the UK was flourishing with the success of the Nuclear Structure Facility at Daresbury Laboratory. To my joy, he was attracted back to Daresbury in 1986, where he has spent the last 19 years. Whilst the NSF was still operational, his experimental skills and knowledge of nuclear models contributed much to the stream of excellent work from the facility. For many of us he was the first stop with any query about models and their interpretation. He struck up strong collaborations with experimenters and theorists. With Mike Bentley he helped map out our understanding of Coulomb effects in N = Z nuclei and with Piet Van Isacker
he again exploited algebraic models to tackle questions related to np-pairing in these nuclei and how it might reveal itself.
In 1993 the Nuclear Structure Facility at Daresbury was closed without regard to the great success of its experimental programme. Dave, like everyone else in the nuclear physics community, was dismayed at such folly but he set about a new task with energy and vigour, namely creating a support group for the UK nuclear physics community. He put together a group of physicists, engineers, electronics and data acquisition specialists which has been vital to maintaining the UK's nuclear physics diaspora. He played a large part in maintaining the community's morale as well. Wherever we gathered, he always insisted on a chorus of 'Always look on the bright side of life' and most of us who knew him will always associate it with him.
One thing he and I shared was a strong belief that in the long term the UK could only maintain its reputation in nuclear physics and an adequate nuclear skills base if the UK built a world-class facility or was officially part of one. I have lost track of the number of papers we have written, together with others, explaining the great opportunities opened up by our new-found ability to create beams of radioactive nuclei. Always we were told that the science case was unassailable but a new excuse for inaction would be offered. Now the entire UK community is united in wanting the UK to join the future FAIR facility at GSI, Darmstadt, and maintaining a presence at GANIL in France. Again, Dave was in the vanguard, helping to make the case at home and representing CCLRC and the UK on the Science and Technology Committee for the new facility. Throughout a decade and more of such efforts, he kept his own science going at the highest level and sustained the efforts of the UK's university groups in their efforts abroad. He had to sacrifice much of his own time and scientific life to do so.
How can one sum up what one felt about him and how much we will miss him? Not so long ago at a funeral in Guildford, the Rabbi's simple message was 'He was a thoroughly good bloke'. That sounds inadequate at first; not many of us merit such an accolade but Dave did. He leaves all of us, Lin, Jenny and Steve, his friends and colleagues, with warm and happy memories. We shall miss him.