Watson was very good in her one film, last winter's arthouse epic Break- ing the Waves, for which she was plucked from the obscurity of "wenching and spear-carrying" (her phrase) at the Royal Shakespeare Company. But the role was an unmistakable one- off - a child-woman, from a straitlaced Highlands community, who so loves her paralysed husband that she lays down her sex-life for him, sleeping with other men and reporting back, mostly into a hand-held camera inches from her nose. An extraordinary debut, the critics agreed: which, in the Hollywood thesaurus, is only a line away from one-hit wonder.
But here she is, just over a year later, in a big studio picture, with her name above the title. Day-Lewis, naturally, is The Boxer. Watson, naturally, is the love interest. But it's a little more complicated than that. He's ex-IRA, just released after 14 years inside, back in the ring and determined to stay off the Semtex; she's his teenage sweetheart, wife of another prisoner, mother of a 10-year-old boy, and daughter of an IRA boss. As if these obstacles were not enough, Day-Lewis is imploding emotionally after his time in solitary, and then there is the IRA custom of placing prisoners' wives on a moral pedestal.
The relationship is measured out in glances, pregnant silences and clipped exchanges, none of which involve clothes being taken off. It's a boxing movie - My Left Hook, as one US magazine put it - but also a love story. From the point of view of Watson's character, it's Brief Encounter with bombs.
And she is excellent again, in a quite different way. She has the stillness and strength required to avoid being blown off the screen by Day-Lewis's coiled intensity. She has a warmth that will make the audience root for her even though her character is male-dominated to an extent that could be a turn-off. She has enough allure to attract a man against his will, but not so much that she is out of place. She is, again, wholly believable playing someone with whom she has practically nothing in common.
"I'M A soft-bellied liberal, me," she says. "A nice English middle-class girl. I've never had to make choices that were that hard."
This was last Saturday, in one of those suites at the Dorchester reserved for visiting sultans and movie publicists. "Very formal," Watson remarked, with distaste, as she sat down on a sofa striped like a cricket-club blazer.
She's fairly smart herself, in a tobacco-pinstripe thigh-length jacket, black sweater and dark-brown slim-fit jeans. She feels the need to explain that all her other clothes are in the wash. She apologises for the fact that it's Saturday (she's been on location all week) and for having a hangover - "I will discover coherence as we go along." There's a playfulness in her eyes and voice which seems to be habitual. So does the sore head: she got to know Jim Sheridan, director of The Boxer, by "comparing hangovers".
She was born in 1967, in Islington, the younger of two daughters of an architect and an English teacher. They lived in Islington long enough for Emily, fresh from the Laura Ashley job ("Oh dear. How embarrassing. I didn't let that slip, did I?"), to become an Arsenal fan. She emits an excellent noise when I mention this: a sort of "aaaaaaaawwwwooooohhh".
"We're not doing so well. Two years running, I've been to a party just before Christmas and everyone's been singing: 'We're Arsenal and we're top of the league.' And then ... "
So what does she make of Arsene Wenger?
She hesitates. "I'm a groupie rather than a serious fan. I fell in love with the boy next door and he was mad about Arsenal, so I was too. I just have this memory of the team going past in an open-top bus when they'd won the cup. I must have been about four."
The Watsons moved soon after that, and kept moving. "I've lived in Isling- ton, Chiswick, Hammersmith, Acton, Kew, Richmond, Brixton, Borough."
They may have been middle-class but they were not conventional. "We didn't have a television and we did strange things like meditation. It was all quite kind of liberal."
Emily went to a private school, St James's in west London, which was so progressive that meditation was on the curriculum. She dreamt of being a poet or an artist and went to Bristol University. It sounds like a charmed life, but there followed several years of the slog every overnight sensation goes through. She was twice turn- ed down by London drama schools; those responsible face a nervous few years waiting to see if they end up looking like the man who turned down the Beatles.
She waitressed, temped, landed the odd role on the fringe, finally got into the Drama School in Ealing, and joined the RSC from there. If she was struggling, she doesn't seem to have thought so herself. "I've never been out of work since I began acting," she said recently. "I've always had this sort of arrogance that makes me think that everything is going to be all right."
BUT EVEN confident people need the breaks. Watson's came when Lars von Trier, the Danish arthouse-extravaganza merchant, was casting Breaking the Waves. Watson had been getting only small roles on big stages, "space- filling" at Stratford and the National, or bigger ones at tiny theatres. The part of Bess, saint and whore rolled into one, was clearly a role- and-a-half, and she would never have got it if Helena Bonham-Carter had not pulled out at the last minute. Watson thought she was crazy, and didn't mind saying so. The subsequent upturn in Bonham-Carter's career suggests she may have made the right decision. There is no disputing whether Watson did. "It was an unusual project. You just had to close your eyes and jump."
When she opened them, she was "paper-thin" from the experience of making a film so harrowing that even some cinemagoers who liked it walked out. As soon as the finished film emerged, she was "kind of a movie star". At Cannes, critics reached for adjectives like "stunning" and "mesmerising". She went on a promotional tour of Europe and America that lasted longer than the shoot.
While standing back from the pro-cess, she threw herself into it. She still says she would do publicity even if it wasn't in the contract. The stream of interviews, each less candid than the one before, was interrupted only by awards ceremonies. "That's fun," she told me last winter, with the full authority of one who had been to at least two of these occasions. "You borrow a frock and la-la about."
She was Most Promising Newcom-er in the Evening Standard Awards, Best Film Actress in the Variety Club Awards and European Actress of the Year in the Felixes. She won Best Actress from the New York Film Critics and the New Generation Award from their counterparts in Los Angeles. At the Oscars, she was up for Best Actress. She kept Madonna (in Evita) and Courtney Love (in The People vs Larry Flynt) out of the nominations, but lost out to Frances McDormand in Fargo: on a night dominated by The English Patient, the Academy needed to honour some of its own. How does Watson remember feeling - dazzled, elated, disappointed? No. "Pissed," she sniggers. "It was just one of those nights, I had a really good time."
The year before, she had got married to Jack Waters, an actor who has worked mainly at Theatr Clwyd in Wales. They met at the RSC, where he was a fellow space-filler. She says he has been "brilliant" about her success; there's certainly a nice picture of them both entering into the spirit of Mira-max's post-Oscars party. And the story goes that the night before Breaking the Waves opened in London, they went to the West End to watch her name go up in lights outside the cinema.
They live in London, when they're not off working, in a small flat which they are trying to leave for something bigger. Her awards occupy a section of the bookshelves. When they move, she'll put them "in the shed".
BETWEEN CEREMONIES, she shot her second film, Metroland, a low- budget (pounds 2.8m) adaptation of Julian Barnes's novel. It will be released, after the distribution delays that dog small British movies, in the spring. She plays the suburban housewife who is the strongest character in this tale of two blokes, from their rites of passage to the first stirrings of midlife crisis. "I liked the fact that she wasn't patronised. She's a wife and mother because that's what she wants, and she's good at it." The character is cool, calm and collected, "with this sort of ironic smile playing on her lips": the closest Watson has been to home.
In The Boxer, her character is patronised. But she didn't hesitate before saying yes. "When Jim Sheridan rings you up and says [she does a Dublin accent, not to be confused with her Belfast one], 'I'm making a film with Daniel Day-Lewis, would you be interested?' you just say, 'Ooh yes.'
"For my generation of actors, Daniel has set a standard of integrity. Every-body knows that Daniel Day-Lewis goes as far as you can go in terms of committing to a part. He's sort of legendary for it. And it's quite difficult to take at times - you have to match him blow for blow."
She was disconcerted to find that Day-Lewis had been walking around with a picture of her in his wallet for months, while going through his now-famous training with Barry McGuigan. On set, he stayed in character, barely speaking to her apart from saying good morning. After My Left Foot and In the Name of the Father, Sheridan says he and Day-Lewis are "like an old married couple". Watson confirms this. She felt further isolated as a woman on a set that was "very tough - a lot of boxing, hard men and politics. I got a bit lonely."
She is now shooting Jackie, the life of the cellist Jacqueline du Pre, who was forced to retire at 28 by multiple sclerosis. Watson worries about doing her justice. "She was sublime. She played with the wisdom of an old man. These recordings that she made when she was 19 were full of passion, compassion and melancholy that she shouldn't have known about at that age."
Having learnt "a huge amount" from Day-Lewis, she is presumably practising the cello round the clock, and well on her way to being among the top 15 players in the country. She laughs, but yes, she has learnt the instrument - "You can't fake it like the piano ... the fear of universal scorn spurred me on. I think I've done quite well."
She now gets offers from Holly-wood but doesn't always know how seriously to take them - "It's hard to tell what the level of engagement is when someone rings up and says, [schmoozy American accent] 'You'd be perfect in this movie'." In three feature films and one TV drama (The Mill on the Floss, in which she played Maggie Tulliver), she has already shown a wide range. "So of course I get offered loads of child-women who sleep around a lot."
'The Boxer' (15) opens on Friday.