In it he received notable assistance from Francis Wormald then Director of the Institute of Historical Research in

(In it he received notable assistance from Francis Wormald, then Director of the Institute of Historical Research in London, of whom he always spoke with particular warmth.) The book's arguments were triumphantly vindicated when a few years later Kurt Weitzmann, in his work on the icons at St Catherine's Monastery on Mount Sinai, found a large number of "crusader" panels which fitted neatly into the schema Buchthal had proposed.Buchthal's publications are remarkable not only for their originality, but for the extraordinary clarity and concision with which they are argued. All the most important are in English, which he spoke with a slight Germanic lilt, and which he took infinite pains to write elegantly. He did his own typing, redrafting with the help of scissors and sticky tape, and further editing in a small but clear and regular script. He worked whenever possible directly from the sources, usually the visual sources, examining manuscripts systematically in libraries throughout Europe and the Near East. He had an extraordinarily acute memory and could call to mind images in manuscripts he had seen 40 years before.

The broad empirical foundation of his work has helped to ensure its continuing relevance.While at the Warburg in London, Buchthal lectured regularly at the Courtauld Institute, and also supervised a few distinguished doctoral students, the first of whom, Professor Michael Kauffmann, was later to become Director of the Courtauld. His relationship with teaching and supervision changed radically, however, when he went to New York in 1965. There he found himself lionised (not to say hounded on occasions) by able and ambitious students who wished to study with him. Established scholars, eager for his advice, also sought him out. His warm response to this enthusiasm endeared him to them to an extraordinary degree.

So many senior posts in medieval and Byzantine art history in US universities are now occupied by his former students, or those who took him as their mentor, that it is hard to believe he was in New York for only 10 years.On returning to London in 1975 he and his devoted wife Maltschi (Amalia, who survived him by only a week) moved into their small terraced house in Highgate, where they lived simply, surrounded by few possessions. They shared a profound enthusiasm for music, and in part through Maltschi's brother, Rudolf Serkin, enjoyed privileged access to many great musicians.Buchthal continued to work with full vigour into his early eighties. His later publications he would describe, with a twinkle, as ``senilia''. But he did eventually cease publishing, anxious perhaps to ensure that all his work would pass the strictest scrutiny.

He remained active, however, receiving publications sent in homage from around the world, and corresponding and conversing on art-historical topics. It was typical that he always wanted to know what people were working on, and when visiting the Warburg would go first to the shelves of new publications.In the house in Highgate is a portrait of Hugo Buchthal aged about 10. He confronts the painter and the viewer with an implacably piercing gaze There is nothing soft or childish about the expression It is unmistakably Buchthal. In his retirement, when I knew him, he could be charming and anecdotal. But I do not suppose that anyone meeting him doubted for a moment that for him the world of scholarship and intellectual endeavour fully merited a lifetime of intense work.The scholars who fled from Nazi persecution were profoundly grateful to their hosts. They sought by their scholarship to repay the welcome they had received, and in the process transformed the world of British academe We have all been beneficiaries.