I once bumped into my dear, late godmother, the painter Lindy Dufferin, at a party at Spencer House, the London home of Princess Diana’s family. Lindy gazed, rapt, at a line of businessmen queuing up to meet Prince Charles, as he then was. “Look—one of them’s actually sweating!” she said. “Why are they so scared?”

Lindy—or the Marchioness of Dufferin and Ava—had complete social confidence. She was the granddaughter of the Duke of Rutland and the daughter of Loel Guinness, an M.P. and hero fighter pilot in World War II. From an early age her life had been laid out along golden tramlines: flung from yacht to yacht with the Swans of Fifth Avenue; shuttling from the smart set in London to golf lessons with Ben Hogan in Palm Beach. She grew up with the likes of Truman Capote (“He was so wicked—I loved him,” Lindy said) and Gloria Guinness, her “It girl” stepmother. With her social X-ray specs she saw straight through rich men’s wealth to the frigid souls that lay beneath.