With 100 films behind her - and a string of high-profile romances - Catherine Deneuve is a movie icon. But, she tells Benjamin Secher, it almost didn't happen.

A slim cigarette smouldering between her fingers, Catherine Deneuve steps into the room that has been scrupulously prepared for her interview, and scowls through her sunglasses.

The great French actress - still profoundly beautiful at 61 - takes one look at the sparse furniture, at the bottles of water lined up like soldiers on the table, at the doily-covered plates laden with biscuits, then turns on her heel and glides back down the corridor, leaving two anxious publicists, one would-be interviewer and a thin plume of smoke trailing in her wake.

For a second, it all makes perfect sense. Deneuve is, after all, a legendarily cool character - a mythically glacial actress forever associated with her early roles as the chilling murderess in Polanski's "Repulsion" or the inscrutable high-class whore in Buñuel's "Belle de jour". Then, coming to an abrupt halt, the woman once described as cinema's "coolest enigmatic blonde" turns to me, peers over her dark glasses and says, in a Gallic whisper as soft and warm as a freshly baked brioche : "Let's go to the bar, non ?"

Within minutes, the actress has commandeered a corner table in the hotel's saloon, and is warming up fast. She puffs out her cheeks in scandalised outrage at the current media frenzy surrounding Kate Moss. "It's disgusting !" she declares, espresso in one hand, biscuit in the other. "I find it so vulgar that the papers should choose to publish those photographs".

She rolls her big green eyes upwards at the thought of hotel heiress Paris Hilton being put on the cover of Vanity Fair magazine. "Unbelievable !" she hisses, conspiratorially. "Who is she but a provocative young Barbie doll ?" The shades are off, the eyes are sparkling and the cliché of the actress as ice queen seems suddenly absurd.

The publication, earlier in the week, of Deneuve's own diaries - in "Close Up and Personal" - had done little to dispel that cliché, concentrating on the humdrum details of days spent on a film set, and skirting the emotional depths of the life of a screen legend. "The things that most affected me", writes the actress in an understatement that sets the tone for the whole book, "don't all feature".

"Well, of course, the diaries are not about private things", she adds now, dismissively. "They're really just about my relation to my work. They were never intended to be published".

The diaries include some wonderful old family photographs and a neat line in celebrity put-downs : Deneuve writes of Mia Farrow that Polanski skilfully "makes use of her shortcomings" ; and depicts Björk as a control freak. But the most remarkable thing about them is the fact that, although they were written, intermittently, over three decades, the author's voice remains incredibly constant from start to finish.

"My character hasn't changed much over the years", says Deneuve. "When I was younger, I was a bit more insouciant, more ignorant, more innocent. Some things have got a little better, some a little worse; but basically I haven't changed".

The outward proof of this internal constancy is Deneuve's phenomenally long-lived career : about 100 films in nearly 50 years, without so much as a pause for breath. ("I breathe cinema", she later says). At an age when most actresses are drawing their pension, Deneuve continues to land leading roles, a feat made even more astonishing by the fact that she never really intended to be an actress in the first place. "It just happened", she says, her narrow shoulders shrugging beneath Prada epaulettes. "It was never a real choice".

Both Deneuve's parents worked in the theatre but initially, of their four daughters, only Françoise, a year Catherine's senior, followed in the family tradition, landing a place at the Paris conservatoire. "Françoise had a very strong personality, whereas I was quite shy", says Deneuve. "Acting was her thing. It didn't really appeal to me - I was more interested in graphic art". Then, in the summer of 1960, Françoise was cast in a film about two sisters (Jacques Poitrenaud's "The door slams") and persuaded her younger sister to audition.

"I was not particularly attracted to the idea", says Deneuve, "but curiosity made me go for it. My mother wasn't too keen, but because shooting fell in the school holiday she let me do it. In retrospect, though, I think I was a little too young".

Deneuve's precocity was not limited to her career. A year later, aged 17, she moved in with her much older lover, the film director, Roger Vadim. "I was very young but I wanted to live my life, you know. At home, we sisters were very close, always together, and I didn't want to live in a group any longer. But I didn't plan to fall in love ; it just happened".

It was for Vadim that Deneuve first dyed her brown hair blonde. "I did it only because I thought it would make me more seductive to the man I loved", she says with surprising frankness. "It seems the silliest thing now, but I was so young and in love".

Before long, Deneuve was also pregnant. "I had always known I wanted to have children very young", she says, "but it didn't start very well. I was separated from Vadim when our son, Christian, was only a few months old. I found myself alone with a child, not even aged 20, and that was very hard".

Only two months after giving birth, Deneuve started filming Jacques Demy's "Umbrellas of Cherbourg", a gorgeous musical folly in which, ironically, she plays a young girl who falls pregnant by a man who then abandons her. Deneuve delivered a luminous performance and realised, with sudden certainty, that acting was her destiny.

Fortunately, there was no shortage of auteurs queuing up to cast the dazzling young Deneuve. In the subsequent four years, Demy was followed by Polanski, Varda, Truffaut and Buñuel.

Then, the year after Buñuel's "Belle de jour" made Deneuve an international star, Françoise was killed in a car crash, aged 25. Deneuve was devastated. Did she ever consider abandoning acting at that point ?

"No, I didn't think like that", she says, her big eyes blinking suddenly. "I had already accepted so many roles, so I just carried on working". She pauses. "I'm not sure now that it was the right thing. But that was the way I sort of overcame…" Deneuve trails off into silence. She lights another cigarette and puffs out a weary cloud of smoke.

Since 1966, Deneuve has worked continuously, turning in a string of exquisitely controlled performances for, among others, Lelouch, Techine, Wargnier (for whose "Indochine" she earned her only Oscar nomination) Oliveira, Ruiz, Von Trier and Ozon.

Compared with her career, her personal life has always run rather less smoothly. Her relationship with Vadim was followed by a seven-year marriage to English photographer David Bailey. "It was very complicated", she admits with a dry laugh. "We didn't speak the same language".

Then there was a very public liaison with Italian actor Marcello Mastroianni, with whom, in 1972, Deneuve had her second child, Chiara. Three years later that relationship also ended badly. "When it comes to falling in love", says Deneuve with a great romantic sigh, "experience doesn't help you in any way".

Two children, two grandchildren, a hundred films and a million fans - her achievements would make most people flush with pride, but Deneuve is having none of it. "As an actress, I can be proud of certain things I have done. But as a person ? No, proud wouldn't be the word. I have never achieved the life I imagined for myself when I was younger". Which was ? "I always vaguely thought I would be in love and living with a man with whom, no matter what happened, I would always be able to talk about things, and always feel supported by. I tried to settle down and have a family, but it didn't happen that way. So, no, I don't think there is anything I can really be very proud of. My relationships have never really lasted very long. I suppose there is something within me that is not right for that way of life".

Deneuve spots the publicist hovering nervously on the other side of the room. The interview has overrun and the actress will be late for her next appointment. Suddenly, the scowl returns, the glasses go back on, the cigarette is extinguished and, in a gush of cool air, one of the world's greatest living actresses sweeps out of the room.