No wonder Naomi Watts looks radiant. She hasn’t worked in “. . . months”, she breathes, her wide blue eyes growing wider. “I've really slowed down, turned down a lot of stuff. This” — she motions to the suite at the Hôtel de Crillon in Paris, where she is being crimped and powdered for her launch as the new face of Thierry Mugler’s perfume Angel — “is basically the only work I’ve done all year. It’s been really nice; the timing has been perfect. I did one movie three months after Sasha was born, and it was very hard. I was breast-feeding him through the day and pumping at night, but . . . ”

But, oh, to be Naomi Watts. A neat, sylph-like figure in Prada gladiator sandals — “bought in the sale!” she trills — and a navy-blue Rag & Bone short suit, another sale buy — “Love my bargains” — she shows no signs of turning down the glamour. Apart from a little jet lag — “Yesterday I was a mess,” she says of her transatlantic journey, boyfriend and sniffly baby in tow — she looks amazing: clear-skinned, naturally pale and blonde, fresh, unplumped, un-Botoxed and impressively lean for a woman who gave birth just a year ago. (And one who might have another on the way. “But I wouldn’t be discussing that in this interview,” she says politely, but pointedly. Her publicist later confirms the pregnancy.)

But then, with a string of huge hits — Mulholland Drive, 21 Grams, King Kong — under her belt, Watts can probably afford to give herself a bit of latitude. After a decade of well-documented Hollywood mountaineering, she has thoroughly earned her position at the top of the A-list pile. The days when she was simply “Nicole Kidman’s best friend” are well past; now Watts is “in movies I want to be in”, she says. And after the second baby’s out of the way, it’ll be straight back in the saddle come spring with The International, a thriller with Clive Owen. Not to mention, at 39, the first big-name beauty contract of her career.

“You feel like you’re getting older and then something like this comes along,” she says. “It makes you feel great.” Chosen, she says, for her “chameleon - like face” and her ability to look “strong in one moment and delicate in another, sometimes angry and forceful, sometimes vulnerable and tragic”, she will also appear in a multimillion-dollar commercial created along the lines of Chanel No 5’s collaboration with Nicole Kidman and Baz Luhrmann. Certainly, it’s refreshing to see proper grown women, rather than wrinkle-free teens, promoting beauty products — accomplished working mothers obviously resonate more with the buying public. “Offers have kept coming in,” she agrees.

And with the imminent renaissance of the Mugler women’s-wear line, Watts is also spearheading a kooky fashion moment. Fêted in the 1980s for his razor-sharp tailoring, shoulder pads and futuristic detail, Mugler’s power suits and hedonistic lifestyle epitomised the hard chic of the decade. In the 1990s, however, the label foundered, but the former Paco Rabanne designer Rosemary Rodriguez has now breathed new life into the brand, with a chic 20-piece collection, including sharply tailored blouses, denim blouson jackets and nipped-in safari dresses.

Watts herself hailed the revival by wearing Mugler to the Costume Institute gala in New York in May, and the new line has so excited the superstylist Katie Grand that she has been carrying around suitcases of his old clothes for inspiration. Mugler himself, who has more or less abandoned fashion in favour of body building, has given it his blessing (and if a recent picture on the internet of him, naked, ripped and proudly showing off alarmingly inflated, waxed genitals, is anything to go by, he won’t be back at the atelier any time soon). “I’ve met him once, in London, and it was great,” says Watts. “We certainly liked each other. He was definitely a pioneer, allowing women to look striking and sexy at the same time and very daring. Young designers all worship him.” She dismisses the suggestion that serious actresses can’t “do” fashion and fragrance. “It’s a good mix. My films go down well in France, starting with Mulholland Drive,” she says of her breakout role in David Lynch’s surreal masterpiece.

If there had been any doubts about Watts’s acting talent, the film’s famous masturbation scene catapulted her firmly into the limelight. It was “probably the most difficult one of my whole life”, says Watts, who only clinched it after a tent was erected around her for privacy. “I just kept crying all the time,” she says. “David wanted an anger, frustration, but I just got weepy. After the third take, I remember saying, ‘I can’t do this, David,’ and he was, like, ‘Okay, Naomi!’ and I was thinking he would [give me a break]. . . but he didn’t . . . and I’d get annoyed.”

Intense, quivering performances have built Watts’s reputation. “I’m definitely a sensitive person,” she says. “I cry at the drop of a hat. But I’m not a victim or weak or anything. I think we all have it, that side. There’s nothing wrong with it. It’s sort of, crack it open!”

One can’t help feeling that her childhood, filled with unsettling experiences, might have encouraged this. She was born in Kent: “I’m English, but it’s complicated,” she says in a delicate Australian accent. “My mother is half-Australian, and we all moved there when I was 14. I feel a big part of me is English, but I am very influenced by Australian culture.” Her father, Peter Watts, a sound engineer for Pink Floyd whose maniacal laugh can famously be heard in The Dark Side of the Moon, died tragically from a suspected heroin overdose when she was seven. “I’ve never known what it is to have a father, but every kid should have two parents.” She has one older brother, a photographer, whom she is close to. “It was very, very sad for both of us at the time. You just deal with it, get used to it.” Has she drawn on this experience in her work? “Of course, I’ve drawn on it,” she says. “I remember details from the day that I was told he died vividly. But otherwise, I have few memories of him.”

As a result, she had a barefoot, hippieish childhood, following her mother and various boyfriends around England before moving to Australia.

“I was horrified,” she says of the upheaval. “At 14, you start creating your peer group. But my mother promised to put me into drama class, so I went.” After school — where she met Kidman — she drifted into modelling and acting in soaps such as Home and Away. Fame did not come swiftly, however. She has had to work for it. “I’m a hard worker,” she says. “Because opportunities came to me much later, there’s an underlying fear that it’s going to go away.”

After a stint of modelling in the Far East, which she hated, she moved to LA to make it as an actress. “Sometimes I did just four or five things a year,” she says. She considered giving up countless times, but every time she got round to packing her bags, “something would come in the nick of time. Oh, for sure, there have been some shockers”, she says of her early roles. “And some even recently. There’s always a risk.” Even now, she still feels nervous. “But feeling nervous is a good thing. Anyone can get famous, but how do you sustain it?”

After a poor love life — “I seem to attract jerks” — in 2002, she quietly started stepping out with Heath Ledger, who was nearly 11 years her junior. They were still in contact at the time of his death earlier this year. “I don’t like talking about it,” she says slowly. “It’s really personal. But he was just . . . It’s all so tragic, just deeply, deeply tragic. He was a wonderful, wonderful person. Words can’t describe it really.”

She is now in a long-term relationship with the father of her child, the actor Liev Schreiber. Marriage? “Maybe, I don’t know,” she says. “I never say never, but I’m not desperate to get married. I’m not someone who has always dreamt of a wedding day. I’m more disbelieving. Or have been.” She pauses. “Well, that was my original stance. You loosen up about things as you get older.”

Such a cautious response seems surprising. But there’s none of the usual gushy rubbish you get from Hollywood stars with Watts — she is a straight-talker, and if the answer is complicated, then the answer is complicated. “I don’t operate in the world of schmoozing and cruising,” she says. Instead, she is pleasantly direct and honest about her conflicting emotions — a maturity that possibly comes from her childhood experiences. It has also been the making of her. She’s is a cool, canny, hard-working operator, a keen deal-broker and bargain- spotter, with the grit to stick at it for 15 years before reaping any rewards.

Watts clearly knows her own mind, and only now, with children, is she just beginning to unwind. What about the future? “Next year is going to be big for me,” she says. “But right now, it’s keeping the family unit together.”

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