The photos, along with snippets of 20 letters, are at the heart of The Diana I Knew, Robertson's fond account of how, while living in London in 1980, she and her husband, an Exxon executive, employed a then-18-year-old nursery school teacher as the family's nanny for 11 months—and entered into a cordial friendship that would endure for 17 years. "I feel I know the very best of Diana," says Robertson, 54 and a homemaker.
Telling the world about her, of course, is another matter. Robertson confirms that Michael Gibbins, Diana's former private secretary, wrote last December to say her book would "increase the difficulties of preserving the dignity of Diana's memory." But the author, who reportedly received five figures for her manuscript, insists her only intent is "to set the record straight. Diana has been criticized and misunderstood in recent years. I did not invade her privacy. I have a completely clear conscience."
A New York doctor's daughter who met her husband at Harvard Business School, Robertson recounts that eight months after the 1979 birth of their first child, Patrick (now a Brown sophomore), the pretty teen in a corduroy jumper arrived through an agency referral. "Here was this lovely, polite young woman standing on my doorstep, giving me that signature look from under her bangs," she says.
Diana remained discreet about her background. It wasn't until Robertson found a bank slip under a couch that she learned that the girl who pitched in with the breakfast dishes—and whom she paid $4.50 an hour—was a titled aristocrat. Soon came a far more startling revelation: A blushing Diana, back from Scotland, informed Robertson that she had spent the weekend at Balmoral with Prince Charles. Still, she wasn't perfect. Once Di ate all the meat from a beef stew intended for guests; other times, after she began dating Charles, she'd call to say she wouldn't make it to work because "I can't bear to face the press today."
During her sometimes rocky courtship, Di turned to Robertson for advice ("I'll simply die if this doesn't work out," she said). But when Robertson's husband, Pat, was transferred back to the U.S. in late 1980, she assumed the friendship was over—until a letter arrived, followed by a gilt-edged wedding invitation. At a prenuptial ball at Buckingham Palace, Di introduced the Robertsons to Charles as "Patrick's parents." (They now also have daughter Caroline, 15.) At the wedding itself, Diana "looked pale and tense," recalls Robertson, who sat across the aisle from Margaret Thatcher, "as if she was hanging on by her fingernails."
Over the years, Diana kept up sporadic correspondence ("Please never stop writing," she implored. "Your letters mean a great deal to me") but never mentioned her disintegrating marriage. Then, last Aug. 31, a friend called at 2 a.m. to tell Robertson that Diana had died. "I felt like my heart really was breaking," says Robertson, who attended the funeral. She plans to donate part of the book's earnings to Di's charities, and she plans to stipulate in her will that the precious letters and cards—complete with crossed-out words, misspellings and Di's trademark happy face—will never see an auction block. "Sometimes you do think things were meant to be," Robertson says of her book. "And I feel I was meant to do this for Diana."
Helene Stapinski in Morristown and Simon Perry in London