In 1938, Peggy Guggenheim was living in London and turning 40. She decided that the moment called for something, so she opened a gallery of modern art, named it Guggenheim Jeune, and launched it with a show of drawings by Jean Cocteau. Over the next 18 months, Guggenheim gave space to Man Ray and Marcel Duchamp while sharpening the eye that would make her one of the century’s great collectors. During those London years her instincts clicked into place. When war loomed, Guggenheim began buying abstract and Surrealist works with near-manic urgency. This exhibition, the first museum show devoted to her British years, revisits that brief but electric chapter. —Elena Clavarino