During the 26 years that Bjørn Wiik spent at DESY, he decisively shaped its destiny as one of the world's major physics centres. He did this in a series of roles ­ leading scientist, HERA project leader, and chairman of the DESY directorate, but most of all as an exceptional scientist and leader whose charm and enthusiasm captivated all who met him. Wiik's calm and soft-spoken manner concealed a penetrating vision and an iron will, which left their mark on world science.

On 7 July 1999, nearly 800 friends and colleagues gathered at DESY to pay a final tribute, both scientific and personal, at a memorial meeting. Among the guests were Wiik's wife and their three children, the Norwegian consul, DESY founding father Willibald Jentschke, and Peter Brix, Wiik's thesis supervisor from Darmstadt.

As emphasized in the opening address by his successor, former DESY research director Albrecht Wagner, Wiik was an outstanding figure in European and world particle physics. His interest and talent extended from theoretical to detector and accelerator physics, all of which benefited from his scientific excellence and uniqueness. Moreover, his impressive political talent allowed him to influence politicians and citizens alike ­ all the more remarkable as a Norwegian at the head of a German national research centre.

As the son of a Norwegian resistance leader during wartime German occupation, Wiik was not exactly predestined for close co-operation with Germany. However, it was his father who urged him to study in Darmstadt to get to know "the other" Germany. One of Wiik's oldest friends, Roland Engfer from Zürich, he remembered the years spent at Darmstadt Technical University ­ the years that allowed Wiik to get to know "the other" Germany, and that laid the foundation of his career as a world leader in particle physics.

After seven profitable years at SLAC in Stanford, Wiik returned to Germany to take up an appointment at DESY, which he felt was the ideal place for him to contribute to physics. Volker Soergel, Wiik's predecessor as head of the DESY directorate, retraced Wiik's time at the laboratory from its very beginning, when Erich Lohrmann heard of the exceptional young physicist and invited him to the Hamburg laboratory in 1972.

Wiik's physics work eventually led him to share the European Physical Society's 1995 High-Energy Physics prize for discovering the first direct evidence of the gluon using the TASSO experiment at the PETRA electron­positron collider in 1979.

From the early 1970s, Wiik nurtured the novel idea of an energy-asymmetric electron­proton collider, a vision that eventually came to fruition with the commissioning of DESY's flagship accelerator, HERA, in 1992.

A talented orchestrator, he led the work for HERA's ambitious superconducting proton ring. Despite DESY's relative inexperience in both superconductivity and proton machines, HERA was completed on time and within budget. Its physics harvest is now surpassing all early promises.

In 1993, Wiik took over from Soergel as DESY's director-general. Under him, DESY's characteristic symbiosis of particle physics laboratory and multidisciplinary synchrotron radiation research centre gained even more importance, the latest achievement being a proposal to set up a structural biology group.

He also played a major role in worldwide efforts to develop the next generation of electron­positron linear colliders, pushing the idea and promoting R&D work for an international 33 km superconducting TESLA machine with integrated X-ray lasers for multidisciplinary research. As Albrecht Wagner put it, Wiik left the particle physics community with a void but also a vision, which is now up to the laboratory to realize.

Hamburg mayor Ortwin Runde valued Bjørn Wiik as a man of high moral integrity, with an exceptional capability to motivate and integrate ­ an outstanding example of his sense of responsibility towards both politicians and the public.

Hermann Schunck, chairman of DESY's Administrative Council, speaking for the Federal Minister for Education and Research (Mrs Bulmahn), called for an effort to make Wiik's ideas and visions become a reality.

Jürgen Lüthje, president of Hamburg University, underlined the exemplary collaboration between DESY and the university.

Detlev Ganten, chairman of the Hermann von Helmholtz Association of National Research Centres (HGF), remembered Wiik as a truly interdisciplinary thinker who promoted the collaboration between the rather disparate HGF institutes with great dedication and judgement.

CERN director-general Luciano Maiani recalled Wiik's valuable collaboration with CERN, as chairman and as a member of the SPS experiments committee on which they served together, and his farsightedness.

Ralph Eichler, chairman of DESY's Scientific Council, closed the first part of the seminar with a more personal view, recollecting many examples of Wiik's practical philosophy ­ like taking the cross-country skiing trail at the Nordic Winter School in the opposite direction to everyone else in order to talk to every workshop participant.

Introducing the scientific part of the seminar, Maury Tigner from Cornell described the impact of superconductivity on particle physics. As well as the HERA proton ring, Wiik also shaped the international effort towards a new generation of electron­positron colliders via the TESLA route.

Rather than dwelling on the past, SLAC director Burt Richter looked at the ongoing role of electron­positron colliders, a field bristling with activity. With science budgets under pressure all over the world, Richter insisted on the necessity to push a single project.

Former CERN director-general Chris Llewellyn Smith recalled the important roles that Wiik had played on various committees at CERN. These included the Scientific Policy Committee, and chairing the 1991 external review of the LHC Project. Further afield he was a key figure in European and world particle physics, particularly in the European Committee for Future Accelerators (ECFA), and in the International Committee for Future Accelerators (ICFA), of which he had been chairman since 1997.

Llewellyn Smith then turned to "deep inelastic scattering" ­ using high-energy beams to reach the deep interior of the proton ­ and the historic steps that ultimately led to HERA.

HERA data have now shed important light on nearly all of the open questions underlined in the milestone 1977 paper by Wiik and Llewellyn Smith, which pointed out the potential of such a collider. HERA's electrons probe protons at an unprecedented level, allowing the interactions between quarks and gluons to be studied in new depth. Photoproduction has revealed the dual behaviour ­ hadronic and point-like ­ of the photon. Neutral and charged current effects vividly demonstrate electroweak unification.

Turning away from particle physics, Jochen Schneider, head of the Hamburg Synchrotron Radiation Laboratory (HASYLAB), presented DESY's second research field, of which Wiik was extremely proud. Synchrotron radiation research has a long tradition at DESY, going back to 1964. Now, with the former electron­positron collider, DORIS, transformed into a dedicated synchrotron radiation source, HASYLAB users ­ including 650 biologists ­ outnumber the particle physicists by far. Wiik felt that DESY was a good place for such a cohabitation, because both fields had a common need in tools, which furthered a fruitful collaboration.

For the future, he envisaged bringing them even closer together within the TESLA project, which includes an X-ray free-electron laser (FEL) for multidisciplinary research. Driven by the superconducting linac, those X-ray FELs will deliver coherent X-ray pulses of between 100 and 300 fs, which far surpass the brilliance of existing synchrotron radiation sources. DESY is building a prototype FEL facility in the vacuum ultraviolet range, to go into test operation in 2002.

Without Wiik, DESY would not be the world focus that it is.