‘Cézanne said he wanted to do Poussin over again after nature,” said the painter RB Kitaj. “I like the idea that one might try to do Cézanne and Degas over again after Auschwitz.” London gallery Piano Nobile has created an intimate exhibition that shows you how Kitaj came to such a conception. It’s the story of an artist who painted history, and a life lived in its shadow. The eeriest image of Jewish suffering here is a tall sliver of a canvas in which a blue-uniformed figure stares officiously, suspiciously, into an open doorway, against gold sunlight. You assume he’s...