Miss Nagel’s wardrobe includes a Madame Vionnet gown, Chanel handbags and many pairs of Manolo Blahnik and Jimmy Choo pumps (“There is nothing incongruent about being brilliant and loving fashion, by the way,” Susan Nagel said. “Reports of John Adams at George Washington’s inauguration show that Adams was dressed in all finery ... Talleyrand loved clothes.”)

Miss Nagel has attended dancing schools (Knickerbocker and Barclay); served as junior chairwoman of charities; and dated a cross section of interesting young men in New York and Europe, including a duke with a castle.

An only child, she was reading “Great Expectations” by third grade, she said. At 12, she was corresponding with Bryan Sykes, professor of human genetics at Oxford University, after becoming intrigued by his DNA research. At 13, she marched into the office of Kitty Gordan, then the upper school director at Nightingale, and announced: “Hello, I’m an eighth grader, I will be here for high school, and I’d like to start a debate team. How do I go about doing that?”

After Miss Nagel wrote up a proposal, the school hired a coach and bought T-shirts. Her older teammates nicknamed her “the baby.”

By her junior year, she was a serious history buff, with special permission to take classes at Columbia University. At her insistence, she and her mother traveled to Orange, Va., one weekend to visit Montpelier, the James and Dolley Madison estate. When the guide said, “Do you know there is no federal monument to James Madison?” Miss Nagel refused to believe it. (“Hadley typically knows more than most docents,” said her mother, recalling a tour of the Tower of London, around 1999. “They were telling some history and she raised her hand and said, ‘Wait, you forgot about Lady Jane Grey and you didn’t know’ that she did this and this and this. And they said, ‘All right miss, would you like a job here?’ ”)