His folkloric surrealism never really changed either, and gained a new lease of life in the post-war revival of interest in myst-icism. Formally, he went on reinventing himself. Happiest with big spaces - theatre designs or murals in chapels - he nevertheless took successfully to lithography, which earned him a lot of money.

Jackie Wullschlager, an art historian herself (she is chief critic for the Financial Times), quotes praise for his early radicalism and criticism of his kitsch, while preserving an admirable distance from her subject. On his emotional life she is equally objective. For an artist he was surprisingly uxorious, per-haps because he was so enormously dependent on women. His sensuality was reserved for his art and he appears to have had no mis-tresses. He married Bella, his Jewish sweet-heart and an aspiring actress, and stayed with her until she died in 1943. In need of an organiser and companion more than a lover, he lived for seven years with Virginia, an Englishwoman, but broke with her when she slept with someone else. Unable to live alone, he finally married Valentine Brodsky ("Vava"), a Russian Jewish woman. All three were managerial types devoted to his genius.

Accounts of his relations with other artists, from Bakst to Picasso, enrich the book. The dandyish Bakst admitted Chagall had talent and allowed him into his art school in St Petersburg, but shook him off in Paris as a potential rival. "I'm not crazy about those cocks and asses and flying violinists and all that folklore, but his canvases are really well painted," Picasso told his lover, Françoise Gilot in the 1950s. After his break with Picasso following an anti-Semitic insult, Chagall inverted the compliment: "What a genius, that Picasso. It's a pity he doesn't paint."