Once upon a time, art sprang like weeds from New York’s garbage-strewn streets, seeding creativity around the world. Scraps of urban decay, along with gleaming shreds of old glamour, fertilised artistic visions. Manhattan in the early 1960s was a sort of modern Medici Florence, producing more excellent art in a handful of years than we have been able to assimilate in the decades since.

There’s a bittersweet reason for that ferment. New York was simultaneously experiencing the trauma of deindustrialisation and spasms of reinvention. The waterfront had a bleary, hungover look and some of its real estate was grungy, ample and cheap — perfect conditions in which to nurture a creative colony. But the city couldn’t afford to stay derelict, and it was never going to be long before steam shovels dislodged artists and bulky new towers replaced walk-ups with rickety fire escapes.