Marianne: Mick's still good to me

She's quite small, quite slim, with a ginormous bosom, like Jordan's, that is swaddled under a glittery black Chanel jacket. Her bottom half is in blue jeans and black patent shoes with bows on, and the only evidence of the slashes she made to her face with a razor blade - when she decided that her looks were the cause of all her problems - is a scatter of tiny pits on her nose.

In fact, at 57, Marianne Faithfull is still remarkably beautiful, with firm skin and the same crushed-velvet eyes and hurt-me lips that seemed to beg for salvation in the Sixties. Right now, though, they have a more prosaic request. "D'you mind if I smoke?" she asks, reaching for her cigarette packet. She grins almost proudly. "These days I go to bed early and I eat properly. I'm not even drinking!"

It's true, if hard to believe. Faithfull, Mick Jagger's ex, one of pop's most famous junkies, has finally got healthy after 40 years of self-destruction. The drugs have gone, the alcohol has gone, she works out with a personal trainer three times a week. She certainly looks good on it, I tell her. "I feel good," she exclaims in her husky, deep voice. "I'm very happy at the moment. I don't think I've ever been happier."

She is sitting on an iron chair with a ratty blue seat in a narrow, shabby dressing room in the Barbican. A plate of hard-looking cookies sweat under clingfilm beside her and the air is sour with smoke. It's not exactly glamorous, darling, but she doesn't seem to mind.

Though she's knackered from a press conference earlier - to promote The Black Rider, the little-known opera by the beat writer William Burroughs she's starring in at the Barbican from next month - she's straightforward and genuinely likeable.

In fact, I'm mystified about her reputation for throwing tantrums. Or rather - to be accurate - I've never seen it myself. When I last interviewed Faithfull, eight years ago, at the rather lonely shell-encrusted cottage she then lived in outside Dublin, she did give the photographer a bit of a hard time, but she also got two local girls in to cook and serve an exquisite lunch that she ate with him and me. The only other person who's been that gracious in eight years of interviewing is Earl Spencer.

Then, I had the impression Faithfull was still a bit in love with Mick Jagger. She admitted poignantly that she felt she should have hung in there and not left him in 1969, and seemed not to have met anyone who had matched up.

But now I don't get that impression, maybe because for the last two years she has been seeing her manager, François Ravard. He ambles up at the end of the interview, a pleasant-looking man of about 50 with a big, drooping paunch, curly black hair and a lived-in, knowledgeable face. They're not married, though two diamond rings glitter from her wedding finger.

"Oh, no!" Faithfull exclaims. "This isn't a wedding ring. It's an eternity ring. And the other one's a diamond ring. I just bought them myself. I mean, I'm also wearing a very beautiful brown diamond cross," she produces it from the depths of her cleavage "but that doesn't mean I'm religious!"

WHAT Faithfull wants to talk about is not her love life, but The Black Rider. This is an opera based on a 19th century German folk tale, the story of a clerk who makes a deal with the devil. Directed by Robert Wilson, the libretto is by Burroughs with a characteristically growly score by the singer Tom Waits.

Faithfull is, predictably, is a mate of Waits and also knew Burroughs. Waits, she says, wrote the song Strange Weather for her in 1989, while Burroughs's heroin-drenched novel The Naked Lunch was the inspiration for her decision to live on the streets as a junkie. You might have thought this would make her flee his stuff like the plague, but apparently not.

"Well, you see," she explains with every appearance of reason, "I completely misunderstood The Naked Lunch when I first read it at 17. I've just been rereading it now and I've realised the prologue is practically a tirade against drugs. I think the first time round I must have not read that." I ponder how different her life might have been had she bothered to get through it at 17.

Back to the opera: it's the first time she's acted for 11 years, and she's very nervous. She had a nightmare that she missed a performance because she was stuck in traffic.

"It was worse than being naked on stage - worse than anything. Though the funny thing is, I've never thought of myself as gone away from acting. It's just that there were never that many parts that were right for me. But this is a really great job and a really great moment for me. We start rehearsing on the 13th, then it's going to San Francisco and Sydney, so I'll be doing this into

And will she finally shake off the Sixties? "I don't know. I've got almost resigned to it. I live in hope!"

How does she feel about that time now? "I feel like it's a big pain in the arse! I would never deny it's part of who I am and, of course, I'm a person of my time, as everyone is, and I wouldn't have missed it for anything - I'm really glad I was there.

"However, it's 40 years ago now. Forty years since my first single, As Tears Go By. Which feels a hell of a long time." Faithfull smooths her thick, highlighted hair.

"And I didn't even enjoy the Sixties that much - I found them very difficult! I was very young, very shy, in what would now be recognised as a very difficult position, though it wasn't then. I was 18 years old, with a baby, anorexia, all these things. Nobody knew, or cared, really, not that it matters now. The point is I got through it and got over it."

She certainly had a lot to get through: the overdose at the end of her time with Jagger (she was in a coma for six days), 15 years on heroin, two of those on the streets, the loss of her only child, Nicholas, after a court case by his father, John Dunbar; three marriages, two abortions and two miscarriages.

Then there was the boyfriend she met at the Hazelden Clinic in Minneapolis while kicking heroin in the mid-Eighties. After she told him they should temporarily separate, he threw himself from a 36th floor window (looking down, she thought his body was a pile of red hibiscus flowers).

Plus there was the weird childhood in Reading - her Viennese mother, Eva, the Baroness Erisso, had been raped by occupying Russian soldiers during the war, and, according to Faithfull's autobiography, may have had an incestuous relationship with her brother, Faithfull's uncle.

EVA worked as a bus conductress and a teacher, and later became alcoholic and attempted suicide. Faithfull's father, Major Glyn Faithfull, was a spy and a bit nuts: his own father, a sexologist, had run off with a dancer from the circus. But she says casually that all these demons have been conquered - "And have been, for a long time."

I ask if she still sees Jagger. "Yes," she says. "Occasionally." Are they still friends? She looks away. "Not really. I see him - if we're in the same town and we're working, I go to the show. I get the best seats in the house and I do go backstage, and I see all of them."

What was it like? "No big deal!" She shakes her head. "Really! He's great, Mick, and I'm very fond of him. He was very, very good to me, and I would be a real c*** if I felt anything else. But it was so long ago. And things have changed - we've all moved on."

But has she? Apart from that first song, As Tears Go By (which Jagger wrote) and her great rage-drenched album in 1979, Broken English, she has never been famous for anything except her ex. She is like Posh Spice would be, circa 2040, if she divorced David Beckham and released one good album.

You have to assume Faithfull has never withdrawn from the spotlight because she liked it, though she would argue that she wanted to make music and needed the cash. But publicity-wise, she has pretty much lived off Jagger since they parted.

But for that great burst of creativity with Broken English, she could be the ultimate ligger. She doesn't see it that way. She takes her work seriously and continues to tour, trooping round the world just like, come to think of it, Jagger himself.

"I've just finished a new record," she explains, "and before that I did a world tour where I did 156 shows over eight months - I went round the world more or less twice. That was to promote my last album, Kissin' Time. And this year I recorded a new album - Before The Poison - in London, which is coming out in September."

François appears. Faithfull gathers up her cigarettes and tucks her quilted Chanel bag on her shoulder. She looks me up and down, smiling approvingly. "I like your coat," she says. "And the shoes. And the scarf." LK Bennett, I tell her. "It's good," she muses. "I like that velour-y look."

Does she see herself a mentor to her fashionista friend, the model Kate Moss. "No!" she exclaims, looking rather embarrassed. "Nor, I'm sure, does Kate." She turns to François. "She asked frivolous questions. But I did manage to talk about the opera." Not too frivolous, I protest.

"Not too frivolous," she agrees, and she and François head through the swing doors, an unlikely couple, but looking quite happy, which for her, has to be pretty much a first.

The Black Rider runs from 17 May at the Barbican Theatre. Information: 020 7638 8891.