I am celebrity-spotting in Michael’s, the Manhattan restaurant that serves as the staff canteen for the New York media business. Tina Brown, who is rushing round town promoting her book on Princess Diana, has phoned through to say she is running late. So I sit and watch as the big names – and some familiar faces I can’t quite place – troop in. By the time Brown arrives, Michael’s is packed and I’m just about the only person in the place I’ve never heard of.

Brown has been a star on this stage since she left London in 1983 to become editor of Vanity Fair. A famously talented networker, she seems to know everybody in the place, from Barry Diller, the internet mogul, in one corner, to Peter Brown, the former Beatles manager, in another.

Wearing a cream MaxMara suit [as the author of The Diana Chronicles would surely observe], she makes slow progress through the room, stopping at several tables to chat. When we finally sit down she is greeted from the next table by Susan Mercandetti, an editor at Brown’s publisher Random House, who is throwing a launch party for her in Washington the next day.

Almost shouting to be heard above the roar of TV anchors at lunch, I say I really enjoyed her book – at least the bits I have read – and that she must be very pleased with the US reviews.

“They have been fabulous. I really didn’t expect it. In life, my goal is just to get away with it,” she says, rather unconvincingly.

Reviewers have praised the book for treating Diana as an important historical figure while sparing none of the lurid details of her life and loves. Brown’s style – People magazine meets The New York Review of Books – also won plaudits, with The Wall Street Journal tickled to find “hottie” and “propinquity” in the same sentence.

“Diana’s was an emblematic life,” Brown says. “The book enabled me to write about a lot more than Diana... about England, the aristocracy, the monarchy, society, the media.”

Diana accelerated the media’s invasive obsession with celebrity, she says. “Diana sold papers like no one has ever sold papers. Once that was perceived it became an absolutely extraordinary phenomenon. The problem now is that there are so many outlets that there aren’t enough real celebrities to go round.”

After ordering (two house salads, plus chicken for her and cod for me), Brown admits that of course she played her part in the growth of the celebrity culture – “but with panache”. At the age of 25 she took on the ailing British society magazine Tatler, which she revived partly by filling the pages with Diana. More controversially, she injected some celebrity glamour into the august New Yorker, where she became editor in 1992, outraging many but delighting more.

In recent years, some of the gloss has rubbed off the Tina story, much to the public glee of her detractors. “Decline and fall. It’s a great narrative arc,” she says, philosophically. She quit The New Yorker in 1998 to set up Talk, a magazine/book/film company backed by Harvey and Bob Weinstein, which closed shortly after the 9/11 attacks hit the advertising market.

Then Brown tried her hand at television with a short-lived weekly talk show on CNBC that was cancelled amid poor reviews and worse ratings.

After these disappointments Brown, now 53, admits the stakes are high. “Writing this book was probably harder than anything I’ve ever done because I was under so much pressure to make sure it was good,” she says, as the waitress removes our mountainous salads, scarcely dented.

She is proud of the book, but also of Talk: “It was very good in the last six months.” She also enjoyed learning the art of television, but concluded that being on camera was not her thing. “I don’t mind being on the air, but I don’t love it. My producer would say ‘flirt with the camera’, but I’m not an actress and I never lost my sense that this was not something I should be doing.”

Not an actress maybe, but doesn’t she do a wicked Diana impression, I ask? She gamely does her party trick, and very good it is too - the lowered head, the fluttering eyelids and the cut-glass accent.

In the book, Brown does not spare Diana, who became increasingly delusional. In their last meeting, a month before her death, Diana told Brown that she thought she could personally solve the problems in Northern Ireland. “But I came out of the book liking her much more than when I began.”

Like Diana, Brown married into royalty, in her case the newspaper variety. Harry Evans, one of the most revered figures in British journalism, had just been made editor of The Times - by its new owner, Rupert Murdoch - when they married in 1981. But Sir Harry, as he is now, was forced out months later and bitterly attacked Murdoch’s stewardship of the paper. He famously claimed Murdoch dismissed the measures put in place to prevent him interfering with The Times’ editorial content as “not worth the paper they are written on”.

So, when I ask Brown about the prospect of Murdoch owning The Wall Street Journal, her reply is hardly surprising: “It would be a horror show. Very sad.” But why would Murdoch do anything to the Journal that would undermine its value? “They said that about The Times.”

She also lays into the Bancroft family, who control Dow Jones, owner of the Journal. Their proposals for preserving the paper’s editorial independence are “absurd”, merely an attempt to “assuage their guilty conscience” for accepting Murdoch’s money. “In two years from now you will run into the Bancrofts wringing their hands like Banquo’s ghost and saying ‘we was duped’ while spending their cheques in Monte Carlo.”

I change the subject and ask who she favours in the US presidential race.

“I’m actually a Gore supporter,” she says, but thinks it unlikely he will run. “He has so much to lose by doing it. Losing in 2000 was a bitter, bitter blow. But he has built himself up from nothing again. If he goes in for it and loses, he will be demolished all over again.”

Brown believes that if Barack Obama becomes the frontrunner for the Democratic nomination, Gore will run. "I think he will think he can win against the unseasoned Obama.” But if Hillary Clinton is in front he will stay out. “I don’t think he would want to take on that whole Clintonian baggage. It’s just bad karma. I think he would find it very distasteful.”

Although Gore is better qualified, Clinton would make a good president, she thinks - particularly in a crisis. “If we were attacked, Hillary would be superb.”

But the fact that Clinton is a woman who is “viscerally disliked” by a large number of voters can’t be ignored. "In a sense, you could argue that she is the only Democrat that can’t win.”

The Republican candidates get short shrift, from Mitt Romney – “Max Headroom” – to Rudy Giuliani, with his “wolverine grin”. John McCain is “my great hero”, but his embrace of Bush and the Iraq war is “going to bury him”.

Brown opposed the war – “I felt so full of dread when we went into Iraq” – although Sir Harry backed the invasion. And she is a big fan of another man buried by his support for the war: Tony Blair. They were contemporaries at Oxford – Blair recalls that he wasn’t glamorous enough to be invited to her famous parties – and Brown believes he is “a very decent man who has done a lot of very good things”.

She is convinced he believed he was doing the right thing by supporting the invasion. “I just don’t quite understand why Blair isn’t angrier with Bush for handling it so incompetently.”

She thinks Blair should also have been tougher with his great friend turned embittered rival, Gordon Brown, who last week achieved his ambition of succeeding Blair as prime minister.

“I think Blair should have taken the bull by the horns and fired Brown by the end of his first term. He missed a chance there.”

Thanks partly to Blair, who she interviewed for the book, she says Britain is now a very different country from the one she left 25 years ago. “London is really humming,” but outside the capital it is a different picture, she says. “The middle classes seem fairly beleaguered and very depressed. They are all talking about moving somewhere else.”

Brown looks at her watch and apologises that she is now running late for her next appointment. I quickly ask about her plans. She has been talked about in relation to some big magazine jobs but says that she can’t think of a magazine that would tempt her. So it will probably be another book, although she doesn’t have a subject yet.

As we shake hands, she gives me such a dazzling smile that I almost think she has enjoyed herself. Then she makes a quick exit. The restaurant is now almost empty, and all the other stars have gone.

David Wighton is the FT’s New York bureau chief

Michael’s Restaurant, West 55th St, New York

2 x house salad

1 x chicken frites

1 x cod with mushrooms

1 x espresso

1 x cappuccino

2 x mineral water

Total: $139.26