Weisz was brought UP in Hampstead Garden Suburb by her mother, a psychotherapist from Vienna, and her father, a Hungarian inventor, and I wonder if the fact that her mother was a psychotherapist has made her think about the way she's bringing up her own child.

"I don't think so, no. For me, being a mum has been a really, really instinctive thing."

As is acting. She's not sure, she says, where the drive to perform sprang from. "I wasn't at all the star of the school play. I wasn't getting up on tables and singing. It was more of a secret, really. I don't know. For me it's all about disappearing. When people think of performing they usually think of show-offs, but I think of it more that you disappear into somebody else."

In fact her teenage years were fairly troubled, though she's reluctant to talk about it. Her parents divorced. She went through three expensive private girls' schools (North London Collegiate and Benenden, before settling at St Paul's). It's usually said that she was expelled from the first two, but the last time the Guardian printed that, her mother wrote in to say it wasn't true. She had, she says, "a problem with authority", and when I point out that in women that's usually to do with an issue with their father, she says, "Goodness! Hmm. I don't know. I don't think there's anything wrong with a bit of healthy disrespect."

Her mother had wanted to be an actress herself in her youth: she was the one who queued for tickets for King Lear at the National on behalf of her daughter in 1986, and seeing it "was one of the reasons I was inspired to act", says Weisz. Seeing, that is, one actor, in particular: Bill Nighy.

"It was just one of the best performances I've seen. It was just like Mick Jagger came on stage or something. It was pretty extraordinary."

And two and a half decades on, she's finally getting the chance to act with him. "I was a fan. A proper fan. I'd go and see him in things and then go backstage and knock on the door and he's always said to me that I liked him before anyone else. And we've always said, 'Let's find something to do together.'

"And we would text each other now and again to say, 'Have you found anything?' And we hadn't. Until David [Hare] offered us Page Eight. So it's been a really long time coming. A couple of decades."

The result is a spy thriller of the sort that simply doesn't get made any more. Or at least, not as this one is, for TV. Nighy is Johnny Worricker, an old-school MI5 agent – decent, uncorrupted, increasingly cast adrift – who's being forced to deal with the realities of the post-Iraq world. It's a big subject – the post-Blairite realpolitik of how a government deals with its own intelligence agencies. And it has a truly stellar cast. As well as Nighy and Weisz, Michael Gambon plays the head of the section, and Ralph Fiennes is the prime minister.

It's Hare's first directorial outing for 14 years, and when it premiered at the Edinburgh Film Festival earlier this year, the Guardian commended the "effortlessly world-weary chemistry between Nighy and Gambon". And Weisz is as magnetic on screen as she always is. It's hard to take your eyes off her, as she inhabits the kind of character that in recent years she's made her own: a woman of passion and commitment. The Guardian, however, noted, that "the 20-year age gap between Nighy and Weisz is the kind of thing that could draw ridicule."

Weisz bristles when I mention this. "I'm not sure how old Bill is. Do you know? I'm 41. You need to Google it. We're not making out. There's one very delicate kiss in the last frame of the film, which is incredibly tender. They connect with their hearts and they have a great amount of empathy. Anyway, I think people of all sorts of different ages can get it on. It doesn't bother me."

Is it my imagination? Or simply a crackly phone line? But, Weisz seems to alternate between full-force charm and a certain belligerent defensiveness. She keeps telling me how great my questions are. And then refusing to answer them.

I try to talk to her about ageing, but turning 40, she says, was "so not a major milestone". And the pressure to look good? "I think as an actor, you have to look after yourself," she says. "It's like being an athlete. You have to look after yourself and work out."

But you haven't felt like you might have to have things lifted or tucked at some point?

"Oh God. Ask me in a few years. I feel a bit too young for that. Maybe I'm deluded. I don't have a philosophical problem with people who do things like that. It's really up to them. But personally, I'll just have to see how I go."

Pretty well, so far; and there's no shortage of roles. After the Oz film, she starts filming on the new Bourne vehicle.

"Are there any family tensions?" I ask. "With Daniel doing James Bond, does it feel disloyal to be doing the other great spy franchise?"

"No. There's no tension. I guess there's a B, an O and an N but they're very different. Bourne is American and I'll be playing American. It's Americana. And Bond is very, very English. I think it's culturally, tonally, very different."

Logistically, though, it's obviously not the easiest thing being two actors in a new relationship, with a young child. Henry will go with her and the nanny to Detroit to film Oz, she says, but he starts school in September. "And I think it will affect things." she says. "It'll be up to him a bit. He might not want to come… I mean so far he comes with a nanny and hangs out on set."

In past interviews, Weisz has said that acting is all about choices: making the right choices, not making the wrong choices. "Well, yes," she says. "Like life. You just never know at the time how things are going to turn out." And she's still, she says, "fiercely" ambitious. But having a school-age child will inevitably affect her choices now. "There are certain things that are now out of the question. Absolutely."

It must be tempting, I say, if you're married to another actor, to do a film together simply so that you can be in the same place for a bit.

"We've already done one. Maybe one day. It's not something we've been thinking about right now. We've been offered some plays."

Is that something you want to do? More theatre?

"Yeah. I'd really love to do a play next year."

Given she won an Olivier award last year for Best Actress for her role in A Streetcar Named Desire at the Donmar, she'll surely get her pick of the parts.

But then things do seem to have a habit of coming her way, although she's astute enough to acknowledge this. At 15, she won a part in a major Hollywood movie, King David, playing opposite Richard Gere, but her father put his foot down and wouldn't let her take it. It wasn't a truly terrible blow, she says, because "I wasn't burning to act. It was something which came later on. It just came my way."

And it would come her way again, after studying at Cambridge. And when I ask her about the struggles of her 20s – she's said in the past that she had problems getting out of bed some days, and underwent a long stint of therapy – she says: "I think moaning about what a hard time I've had in my 20s would be pretty bad taste. I've had a very privileged life, wouldn't you say? Looking at it from the outside? It looks pretty good, doesn't it?"

It does. Although, when I listen to the tape later, I can't quite catch the tone of this. She has, admittedly, recently shacked up with James Bond, but anyone who's just come out of a nine-year relationship and divorced the father of their child hasn't had it all roses, have they?

Is she being ironic? Or just super-literal? I'm really not sure. But I suspect that looking at Rachel Weisz from the outside is now probably the closest anybody is going to get.

Amazing the difference a year makes in Fest-time.

Or two. Or six.

A It seems like just the day before yesterday, but really it was 2005, that Madonna came to town with her husband (who's no longer), stepping out on Wellington to a restaurant, Nectar (that's no longer), playing The Good Wife in an arm-sling (a product of a mid-decade horse injury, if you recall). "Even Madonna can't save Ritchie from the critics," went the predictable singsong-y schadenfreude, and, specifically, in an article in The Daily Telegraph thereabouts, whilst the sharks circled and circled Guy's flick, Revolver. And that was that.

There was also that time, TIFF-wise, when then-happy couple Jennifer Lopez and Marc Anthony put on one of the boogie-iest parties that our annual Toronto bacchanal has ever seen. Making the scene at a post-premiere party in The Distillery for their he-she El Cantante, the husband/wife duo did something more than just stand around, in repose, daring not to move a hair for fear of a bad photo: they salsa'ed. For about an hour! "Sometime or another, after midnight had already corked," I wrote back then, "sixtysomething Mama Lopez" - Jennifer's mom! - found her rhythm, too, dancing like "a twisted flame," with some "breakdancing strokes" and "limbo," too.

A family affair, the whole thing was. And that was that.

The ties that bind were also being flaunted just, well, 12 months ago when the great, wily, sly, gravitas-dripping Rachel Weisz arrived at Roy Thomson Hall with long-time partner Darren Aronofsky in the name of his potboiler Black Swan. A black-and-white scheme was concocted, dresswise. A smile was hatched, one that matched the one creeping over the face of her auteursweetheart. The red carpet was walked splendidly. But what lurked/lurks behind the masks that are put on by any of the screen-meisters who must walk the carpet, and talk that walk, during the high-stakes culture of celebrity-maintenance during TIFF?

One year and the pull of an alternate life later - Weisz surprise-plunged into the river of marriage with Daniel Craig earlier this year - the Oscarnominated actress scoots to town now with not just a new relationship under her belt, but one, two, three (!) movies. "Rachel Weisz's year," is how Indiewire.com sizes it up - and who are we to contest it? Here to tri-premiere, she's got The Deep Blue Sea (a romantic drama lensed by Terence Davies), 360 (another torcher, c/o Fernando Meirelles, the guy who previously directed The Constant Gardener), and the Festival's curtain-closer, Page Eight (a spy thriller brought to Toronto by the esteemed David Hare).

But will James Bond be by her side here - once, twice, if not thrice? Not out of the realm of possibility, for in terms of the see/be-seen policies that some showbiz couples adhere to, this is a partnership even when it comes to moviepeddling. Last month, Craig appeared, he did, at the premiere of Weisz's just-out (and otherwise acclaimed) Whistleblower in New York City, making it known that as far as their celebrity union goes, they were titling more towards Brangelina (who very often support each other at each other's premieres) than, say, Gwyneth Paltrow-Chris Martin, who have to this day never walked a carpet together (she once called the concept "cheesy").

How much to let the media in, if at all, and how to get the vampires out when you've already extended the invite into your den? How to avoid a tootwee portrait of joint-at-thehip-ness without it sending the wrong message about your relationship? How much? Too much? The politics of red carpeting is just that: political. And - get this - there ain't no universal guidebook.

The Fest, as it is, will have many test-cases of this, as the circus gets going on next week. Take, for instance, Hysteria, a naughty film about the real-life inventor of the vibrator that's world-premiere'ing here and stars both Hugh Dancy (who's married to Claire Danes) as well as Maggie Gyllenhaal (who's married to Peter Sarsgaard). Will it be a date for four at Roy Thomson Hall?

But back to Weisz: how, if at all, have things changed since the recent man-upgrade? "No, I haven't felt hunted at all," she insisted to the Observer, in the U.K., last week, when asked if the universe had shifted since becoming part of an "extremely famous couple?"

"Maybe I'm just not interesting enough," Weisz said, piling on the humility.

It's a full circle in other ways for the dark-haired wonder, oh by the way. Rachel and Daniel came to be, it's true, when they were in Ontario fairly recently shooting a film called The Dream House. The madeinCanada production had them playing husband and wife, which eventually led to the mirroring in real life, and led to Rachel shedding Darren whilst Craig said bye to his own longtime girlfriend, Satsuki.

Secrecy was evidently the name of the game, as that film's executive producer confirms. Talking to Entertainment Weekly a little while ago, Rick Nicita said about the on-off-screen newlyweds, "As far as I can tell, it took everyone on our film by surprise. They were very, very discreet on the set."

Translation: One never does know what's going to happen in celebrity-land.