In your book, Diana comes off as a complicated, compromised person. On the one hand, she's a brave and funny woman who stands up to Britain's elite. On the other hand, she's smug, manipulative, and paranoid—a woman who runs after unsuitable rich

BARELY LEGAL Diana, 19, shortly after her engagement to the Prince of Wales

In your book, Diana comes off as a complicated, compromised person. On the one hand, she's a brave and funny woman who stands up to Britain's elite. On the other hand, she's smug, manipulative, and paranoid—a woman who runs after unsuitable rich guys and regularly sweeps Kensington Palace for bugs. Which one is the real Diana?
Diana was a very sweet, undereducated, slightly confused girl who then collided with this very unforgiving culture with the Windsors. I think it was toxic for her. If she was a little insecure before, the Windsors made her paranoid. If she felt unloved as a child, the Windsors made her feel utterly rejected. It was one those things where nothing could have been worse. This was a girl who had always wanted a mother, so she turned to older women for mentors. But quite frankly, if you're looking for a sweet, touchy-feely mother substitute, Queen Elizabeth II, for all her admirable qualities, is hardly the person you'd turn to.

Though your book largely portrays her as naive and kind of dumb, Diana seemed to be very savvy when it suited her. You contend that she was angling to marry Prince Charles ever since she was a teenager.
She did have this incredible EQ. The very first thing that she said to Charles on that first picnic when they were thrown together was very shrewd. She said, "You looked so sad when I saw you at the funeral of Lord Mountbatten." And it went straight to the mark, because it said to him immediately: "Here is a caring and sensitive girl who, amidst all of the pomp and circumstance at the funeral, saw that I, Charles, was lonely and melancholy." She always managed to say the right thing. She was brilliant at it actually.

In England and across the world, there's a public, largely heroic image of Princess Diana, which is contradicted by the portrait painted by some of her closest confidantes. While researching your book, you had access to several of her tightest friends and advisers. What's their evaluation of her?
There are still people who feel burned by Diana, and they will tell you that she became immensely capricious and vindictive as her life became more and more that of a superstar, and she got a little crazier as the divorce started to happen. That was when, for instance, she got this absolutely obsessive idea that Charles was having an affair with the children's nanny, Tiggy Legge-Bourke. Diana spread around that Tiggy was pregnant by Charles, and at a party she went up to her and said, in front of the group of 50 people, "Oh, I'm so sorry you lost the baby, Tiggy."

No way!
This was the kind of thing Diana was doing in those years before the divorce. It was a divorce that was as crazy as Alec Baldwin and Kim Basinger's. Think about it in those terms.

What was the most surprising thing you discovered about her?
I was really quite surprised at the extent her nerve, her sheer kind of calculated, courageous, reckless nerve. Like when she wanted to do the Martin Bashir [BBC] interview she knew that she would never get the palace to consent to do it, so she got Martin Bashir to smuggle the cameras up to her suite at Kensington Palace disguised as hi-fi boxes. One of the people who worked on the show told me she was like a coproducer of the entire segment and knew exactly what she wanted. She wanted to look tragic and haunted. So she did her own makeup, making her face extremely pale and putting big shadows under her eyes. I wasn't aware that she was quite that savvy about stuff.

DRAMA QUEEN In 1995, Diana told the BBC's Martin Bashir that she self-injured, had suffered from bulimia, and that, because of Camilla Parker Bowles, "there were three of us in this marriage, so it was a bit crowded"

Media savvy, too.
Genius. She was inconceivably media savvy. When Diana was going to cooperate with Andrew Morton for his book on her, she lied to everybody. I mean, just stared them blind. Prince Philip and the Queen had her up to the castle and said, "We know you've cooperated with this book," and she said, "Absolutely not. Andrew who? I have no idea what you're talking about." Meanwhile, she was negotiating the book for serial rights.

Another time, she discovered that a woman called Lady Colin Campbell was writing a book that was going to show her in an unfavorable light and threatened to totally take the shine out of Andrew Morton's hagiography. So Diana decided to leak news of Fergie's divorce to deflect attention from herself. At the time, Fergie was in the middle of a very quiet divorce from Prince Andrew, but when news of her split hit the newspapers it completely drowned out Lady Colin Campbell's book, which was exactly how Diana planned it.

And yet most people in Britain believe that not only was she a heroine, but that the royal family knocked her off.
Yeah, they do believe that. These devious tricks Diana did were not particularly attractive, but by the end of this book I still liked her a hell of a lot more than anyone else in the sad story. She was genuinely compassionate and caring, too. She was up against so many lies and such treachery. She basically fought back with the only thing she had, which was a bit of lies and treachery of her own.

You've been pretty firm in your belief that Diana's death was an accident.
I can understand why people feel she might have been murdered, because it's unbearable to think that someone so special died in such a banal way, but the truth is that night was an accident. She was in a car with a drunk driver wearing no seatbelt and driving at 75 miles an hour into the most dangerous tunnel in Paris. The car was found in the tunnel smashed into a pillar. She bounced off, and she died. All their movements that night were too erratic for it to have been a murder.