His subjects were highly specific, and he painted them again and again, sometimes for years on end. The main ones were his family and friends, or models who became friends; the many glories of London (its pedestrians, its streets, its railway and underground stations and their trains); and old master paintings in the National Gallery. One motif for several years around 1970 was a public pool roiling with schoolchildren. His active surfaces had precedent in artists ranging from Rembrandt to Constable to van Gogh to Chaim Soutine and Willem de Kooning.

Mr. Kossoff’s work was closest in appearance and spirit to that of the German-born British painter Frank Auerbach, five years his junior and a close friend during their early years. Like Mr. Kossoff, Mr. Auerbach favored a loaded brush and dense surfaces that conveyed both anxiety and largess. They both painted construction sites that sprang up around London as it rebuilt from the Blitz, and they were both indifferent to the distinction between abstraction and representation.

Mr. Kossoff and Mr. Auerbach were students together at St. Martin’s School of Art and the Royal College of Art and attended a class at Borough Polytechnic taught by the prominent British modernist painter David Bomberg, a dynamic teacher. They both had their first exhibition at the Beaux Arts Gallery in London in the mid-1950s; represented Britain in the Venice Biennale (Mr. Auerbach in 1986, Mr. Kossoff in 1995); and declined honors from the queen. And both were overshadowed in prominence by their contemporary, the realist painter Lucian Freud, who had a much more sensational personal history and a flashier painting style. In recent years, this imbalance has begun to correct itself.

Mr. Kossoff was a very private man, strikingly modest if not self-effacing. Yet he was uncompromising in his work, as reluctant to welcome visitors to his studio as he was to let paintings leave it.