What Kate did next

The outfit is American girl about town - floaty top, cargo pants and dangerously high suede mules - but the words coming out of Kate Beckinsale's mouth couldn't be more English in their understatement. The actress has just been asked about falling in love with Len Wiseman, director of her new film

We talk on the phone all the time.'

Still, it's clear that this friendly, forthright and down-to-earth beauty ('I don't do facials') is anguished by her tabloid pursuers. Not even her baptism of fire as the heroine of 2001's critically savaged Pearl Harbor was preparation enough. 'Before this happened, I'd lead such a quiet personal life. You know if you go to a premiere, you will get photographed.

But as soon as Mike and I split up and Len and I got together, well - I'm really finding my feet with it. I've been followed by three vans of photographers and it freaks me out, especially when I have Lily with me.'

The mention of her child brings a wide, warm smile. 'Lily has parents who love each other and love her. I'm proud of us for that. I know everyone thinks, "Oh, Hollywood people are always jumping in and out of bed with each other." But I was with Michael for eight years. Lily is great --and she knows that there's this thingcum-monster called Kate Beckinsale that I have to do occasionally.'

Today is one of the days that this 'thingcum-monster' has to perform its public duties.

Underworld, a tale of contemporary leatherclad vampires battling old-fashioned hairy werewolves, is the first film to carry Beckinsale's name exclusively above the title, and she's out banging the drum for the movie she nearly passed on. Of course, had she said no, she wouldn't have met Wiseman - the sort of life-changing encounter Beckinsale had (ironically) already enacted on screen in Serendipity, a romantic comedy about how fate provides your soul mate.

'I thought, "A vampire movie? That sounds so crap." But one day the script flipped open and inside were all these incredible drawings Len had done of Selene, the queen of the vampires. My mum said, "Look, they've drawn pictures of you to get you to read it." I thought they couldn't possibly have, but when I looked at them even I thought they looked like me.'

When she met Wiseman, Beckinsale discovered he'd done the pictures four years previously. 'I do find it shocking when you meet the right person how extraordinary it is that you met them at all. And when you meet your absolute match, it's even more shocking. I just think, "Jesus, what if I hadn't done the movie?" It's terrifying to think that.'

The word is that not only will Underworld be a hit but that it could also be the start of a franchise - Beckinsale's dark version of Lara Croft and a chance to reach the Hollywood A-list after making more than her fair share of high art, low-budget indie fare, from Merchant Ivory's The Golden Bowl to the nameless project that had her urinating into the Thermos of the director who'd bullied her in to doing a nude scene. It's a nice present for a girl who's recently turned 30. 'I went to bed thinking, "Oh f***, I'm going to be 30," but woke up relieved my twenties were over,' she laughs. 'Your twenties are really quite turbulent.'

It's all a long way from her debut in the TV movie One Against The Wind in 1991. A part in Kenneth Branagh's Much Ado About Nothing while she was still at Oxford followed, but it was a BBC adaptation of Cold Comfort Farm in 1995 that put her on the map on both sides of the Atlantic. The fact that she's remained in the US may have less to do with work and more to do with the fact that no one there knows, or cares, that she's the daughter of British sitcom stalwart Richard Beckinsale, who died of a heart attack at 31, leaving a shattered five-yearold behind. Beckinsale adored her dad but he cast a long shadow for a long time, particularly in her teenage years when anorexia withered her to five stone. 'It stayed with me, that huge loss,' she says. 'I expected bad things to happen, that friends will leave, that loved ones will die. It manifested itself as anorexia.'

Beckinsale's in terrific shape now. 'Yes, I'm very athletic in Underworld, which is ironic because I was always the girl at school with the complicated hairstyle who wanted to bunk off PE to go and smoke fags. When they heard about this film, my brothers [she has five step-siblings from the remarriage of her mother, English actress Judy Loe, and a half-sister, actress Samantha Beckinsale] were all laughing at the thought of me even running. But I did start working out after Pearl Harbor and I've actually grown to like it.' Careerwise, she's past the English rose stage, playing Ava Gardner in Martin Scorsese's The Aviator, the Howard Hughes biopic with Leonardo DiCaprio, which is already generating advance Oscars buzz.