I first met Claude Chabauty in the autumn of 1963 in Paris. My military service was to finish in six months and my thesis supervisor, Francis Châtelet, had recommended me to him as a senior lecturer of mathematics at Grenoble. Claude Chabauty received me in the Paris apartment of one of his brothers-in-law. I was right away struck by his unpretentious manner, his warmth and down-to-earth nature. Our short hour of conversation convinced me to apply to Grenoble where I was sure of finding a mentor, broad-minded and pragmatic, who was guided by ideas tested over time, as well as being a man of learning. I was ready to return to my home town and to admire this great man of science. From favourable rumours, I knew that he was one of the rare provincials respected by the Parisian mathematicians. He was to influence the rest of my career profoundly. For 14 years, we worked side by side, where he remained a "walking" reference, often consulted.

To understand the moral authority of Claude Chabauty, it is necessary to outline his mathematical life. He entered the Ecole in 1929, and achieved agrégation in 1932. He did his military service in the artillery and then did his practical teaching at the Faulty of Sciences in Paris. He went to Princeton for two years, before returning as a resident of the Thiers Foundation. During this period he developed the results which were to be collected in his thesis, defended in 1938. In it, he demonstrated his ability to break new ground by marrying the geometry of numbers and p-adic analysis to obtain profound results concerning rational points on curves or algebraic varieties. For 20 years, he followed this original and difficult direction where, thanks to his talent, he extended the work of Mahler, Siegel and Thue. To appreciate the impact of these results, I shall cite only one fact: the theorems proved by Claude Chabauty in his thesis were improved only in 1970, after numerous unfruitful attempts.

Shortly after the war and demobilisation, Claude Chabauty was appointed to the Faculty of Sciences at Strasbourg, that had folded for the duration of the war at Clermont-Ferrand. He was promoted to professor, without a chair, in January 1946 and then professor, with a personal title, a year later. As early as 1949, at less than 40 years of age, he was awarded, the chair of rational mechanics. In 1954, he was a candidate for the chair of differential and integral calculus at the Faculty of Sciences of Grenoble. He was readily elected to succeed Marcel Brelot (1924, .. ) and in a quarter of a century, he transformed mathematics at Grenoble completely.

He created the laboratory associated with CNRS first. He was aware, at a time when mathematicians cared little about it, of the need to appoint quality technical and administrative staff, necessary for its operation. Under his direction, the group of mathematicians was greatly revitalized. The construction of the buildings on the university campus of Saint-Martin-d'Hères afforded an opportunity to give pure mathematicians an exceptional working environment that has become the Fourier Institute. This included a library that benefited from hundreds of exchanges, that are worth the responsibility and the distribution of the Annales internationally, well-designed teaching rooms and offices where it is good to work. How many buildings, constructed and fitted out in the sixties, retain a level of comfort, 25 years later, that is worthy of the best anglo-saxon universities?

With the support of these work facilities, unique in France, where he could shelter from envy, Claude Chabauty directed the starting up phase of the services of the Institute for Teaching in Secondary Schools (Institut Préparatoire aux Enseignements du Second degré) that he had agreed to manage. He also developed a forward looking policy of recruitment: he did his best during the mad years of expansion to acquire positions ready for the future. When the difficult years arrived, the demographic pyramid was better balanced than in most of the French mathematical institutes.

At the same time, his example and the warm environment that he had cultivated has aroused in many young people a vocation for mathematics. Around ten of them now occupy important positions in other university cities, owing to a deliberate policy of refusing internal promotions. The results of this attitude are rapidly seen: during the 70s, Grenoble had the best provincial Department of Mathematics alongside that of Strasbourg; it led with lively, quality research; it attracted numerous events and prestigious conferences to the capital of the Alps; it recruited high calibre staff. Once at the Consultative Committee of Universities where the provinces readily complain of the domination of Paris, I even heard it said, that "Grenoble was the conscience of Paris".

Perhaps it is necessary to look on the other side of the coin and, at Saint-Martin-D'Hères more than elsewhere, at the widening of the gap between pure mathematics on the one hand and applied mathematics and computing, on the other. Have the different policies of recruitment, such as the different conditions of work, not accelerated the drifting apart of the two communities that spring from a common origin?

Claude Chabauty has exercised his academic leadership with much skill and understanding. Favouring personal contacts, he had an exceptional gift for getting outcomes that were both clear and agreed by consensus. Each spring I have seen him prepare with the same mastery the distribution of teaching and responsibilities for the following academic year, the recruitment of new colleagues and the hierarchy of priorities.

Each time the starting situation seemed inextricable, each time agreement emerged after some weeks of revision and dedication spent privately in his office. This office, that we have wanted, had its walls entirely panelled with the Brazilian rosewood; this office, where he had filled the shelves with antique books, lent itself marvellously to personal conversations where Claude Chabauty drove away the doubting spirit of an unhappy researcher, reassured a colleague whose teaching was giving rise to whispering in the lecture theatre, calmed the impetuous zeal of the young, pushed lecturers wilting under their load towards the giving up of certain responsibilities, listening to the grievances of the secretaries who were at the mercy of the rampant individualism of the mathematical researcher. He embodied wonderfully the community of the Grenoble pure mathematicians and knew how to find a compromise, without blandness, between the different approaches. His experience, calmness, sure judgement, his ability to step back, the weight of his contempt for mediocrity, were imposed on all.

In 1968, the turmoil passed without causing damage: the policy of intelligent reforms upheld by Claude Chabauty had deprived all the brutal protests against the system of oxygen. This was unquestionably very enlightened paternalism.

His culture, together with a fabulous memory, impressed his peers and younger colleagues even more than his mathematical knowledge. At the end of his career he wished to complete it by rereading Plato and resolved to go through the Drômoise hills, armed with a telescope to observe the sky. Destiny was to allow him 10 more years to realise these projects.

On his retirement, the Institute Fourier bestowed an exceptional honour on its founder by dedicating a volume of its Annales to him. As his new life, shared between Dieulefit and Grenoble was commencing, it was as if everyone was evaluating how much the golden age of the Institute Fourier owed to him.

Jean-Jacques Payan