Peter will be remembered by all who knew him as a remarkable scientist, communicator and educator who made fundamental and ground-breaking progress in the world of electron optics, aberrations and digital imaging.

Peter’s first foray into electron microscopy and into electron optics in particular was when as a fresh graduate student in 1959 he joined the ‘Electron Microscopy Group’ headed by Ellis Cosslett in the Physics Department of the University of Cambridge. At that time the Physics Department was still occupying the historic Cavendish Laboratory in the middle of Cambridge, where both the electron and neutron were first discovered (by Thomson and Chadwick, respectively).

Peter’s interest and expertise in both physics and mathematics made him an ideal PhD candidate to study the fundamentals of electron optics. Cosslett gave Peter a series of papers by the mathematician Peter Sturrock – who had completed his PhD with Cosslett a few years previously – and told him to apply Sturrock’s eikonal methods to the aberrations of quadrupoles and related multipole lenses. Peter focussed in particular on the relationship between system symmetry and permitted aberrations, with the ultimate goal of proposing ways to correct for lens aberrations, and, in particular, the dominant spherical aberration of round lenses. He discovered that whilst quadrupoles have an unwanted linear focussing effect, sextupoles have no linear focussing effect and have aberrations of exactly the same nature as the spherical aberration of round lenses. Unfortunately sextupoles do suffer from second-order effects and that was sufficiently problematic that Peter did not pursue the sextupole design further. Of course, some years later, first Beck and then Crewe, Rose and others, showed that sextupole doublets could indeed provide correction.

After his PhD, Peter remained in Cosslett’s group as a post-doctoral Research Fellow funded through a number of different institutions. Peter has written of his time both at Peterhouse and Churchill College, two of the Cambridge colleges where Peter was a Fellow, with great affection. He revelled in college life, mixing with other academics across many disciplines, not just in Physics or Mathematics, but also biology, philosophy, history and archaeology. He would tell of his time on the wine committee at Churchill, with the ‘demanding’ job of tasting and buying quantities of wine to lay down in the college’s large wine cellars.

Peter continued to work in the area of electron optics with Cosslett and his group throughout the 1960s and the first half on the 1970s. His work was stimulated through breakthroughs, for example, by Deltrap, showing quadrupoles and octopoles can correct spherical aberration, and by Hardy demonstrating the correction of chromatic aberration.

In 1966, together with other experts in electron optics from around the world, Peter spent a month at Argonne National Laboratory in the US, at a workshop organised by Albert Crewe. The workshop was there to design a high voltage aberration-corrected microscope, which led to a proposal to the US government. Unfortunately, the proposal was not funded – perhaps it was too far ahead of its time.

During the 1960s computers were beginning to make their mark in the world of electron microscopy, initially in the design of new electron optical systems. Towards the end of that decade Peter proposed to Cosslett that the group needed to also embrace the ideas of computer-based digital image processing (of electron micrographs) and consider purchasing a mini-computer to enable this. Cosslett suggested Peter apply for funds, which he duly did; the proposal was successful and a PDP-8 was acquired. The PDP-8 computer had 20 kilobytes of memory – tiny by today’s standards - and was about as large as a family fridge! Using this computer, Owen Saxton, who joined the Cosslett group in 1970, together with Ralph Gerchberg, devised the Gerchberg-Saxton algorithm to solve the ‘phase problem’ by using an image and diffraction pattern from the same specimen area; this remarkably successful approach has now spread across many scientific fields.

By 1974 the Physics Department in Cambridge was due to move out of town to a new building, the ‘New Cavendish’, in west Cambridge. Also, Cosslett was due to retire in 1975 and so there was a great deal of uncertainty as to how the Electron Microscope group would evolve. At that time, Peter received a letter from Bernard Jouffrey inviting him to join the CNRS Laboratory of Electron Optics (now CEMES) and set up a new research area in image processing. Toulouse was the home of the world’s first high voltage electron microscope and remains an important centre for electron microscopy development to this day. Peter took up the invitation, his application to the CNRS was successful, and he left Cambridge for Toulouse in 1975. He remained at the Toulouse Laboratory, becoming Director in 1987, until his retirement in 2002, when he became Emeritus Director of Research.

Throughout his career, Peter was a prolific writer of articles, books and reviews. His first book, on ‘Quadrupole Optics’ was published in 1966, with many others published over the next 50 years or so. Peter’s collaboration with John Spence led to the books ‘Science of Microscopy’ and ‘Springer Handbook of Microscopy’. In the 1980s Peter began work on his seminal multi-volume book, with Erwin Kasper, ‘Principles of Electron Optics’, published first in 1989 with a second edition in 2017, the book’s name paying homage to Wolf’s ‘Principles of Optics’, a book which Peter thought to be one of the very best. He has written extensively on the history of electron microscopy and electron optics, including the history and development of aberration-corrected microscopes.

In addition to his own research papers Peter would regularly publish wonderful ‘round-ups’ of key papers from the microscopy world, and key talks that had been given at major microscopy conferences. These were published in the journal Ultramicroscopy with Elmar Zeitler as its Founding Editor-in-Chief. One of Peter’s early publications in that journal was a poem in response to a call for a better journal title! Peter kept a strong connection with the journal throughout his career, and with its Editors (following Zeitler there was Kruit, Midgley and now Kirkland) and his ‘round-ups’ were always entertaining and keenly anticipated.

Peter was also, from 1982, the Editor-in-Chief (more recently joint Editor) of Advances in Electronics and Electron Physics (now known as Advances in Imaging and Electron Physics) – a highly successful book series that has highlighted, through substantial review articles, the key developments across a wide range of subject matter. He served on the Editorial Boards of many journals including Ultramicroscopy, Journal of Microscopy and Journal of Mathematical Imaging and Vision.

Peter had many awards and prizes bestowed upon him over the years including a Doctor of Science from University of Cambridge in 1980, honorary membership of the French Microscopy Society, Fellowship of the Optical Society of America, Fellowship of the Microscopy Society of America and Fellowship of the Royal Microscopical Society. He was awarded the CNRS Silver Medal in 1983.

Peter’s desire to bring communities together is reflected in other activities. In 1980, together with Hermann Wollnik and Karl Brown, he established the quadrennial International Congress on Charged Particle Optics, bringing together scientists from the worlds of electron optics, accelerator science and spectroscopy. He was involved in a number of international microscopy congresses and three Pfefferkorn conferences.

It seems fitting to end though by highlighting Peter’s extraordinary influence on European microscopy as a whole. In 1998, it was recognised that a new pan-European society should be established and Peter became the Founding President of the European Microscopy Society. Since those times, the Society has gone from strength to strength but it owes a great debt of gratitude to Peter and those on the Executive Board at the time for their vision and founding principles.

Beyond all his professional achievements, Peter was known for his kindness, humility, and unwavering commitment to scientific excellence. His legacy will continue to inspire future generations of scientists and researchers.

Peter Hawkes will be deeply missed, but his contributions to science and his impact on those who knew him will live on.

The European Microscopy Society extends its condolences to Peter's family and loved ones.