He knew she was right the minute she walked into the audition.

Peter O'Toole says: 'I looked down and saw the name Tara Fitzgerald on the list, and when I looked up and saw her, it just went "ping" in my head. We were hoping someone would come through the door with IT! And Tara certainly had IT!'

Tara Fitzgerald, 24, blushes when the tale is recounted. But anyone who enjoyed her passionate romps in the small-screen adaptations of The Camomile Lawn and Anglo-Saxon Attitudes, and in the British hit film Hear My Song, about the Irish tenor Josef Locke, will share some of O'Toole's enthusiasm.

He was part of a committee of four men who cast Tara in Keith Waterhouse's Our Song, a funny, but ultimately tragic, new play about the traumas of an illicit affair.

The production, based on Waterhouse's 1988 novel, opens in London's West End tonight at the Apollo Theatre. It's one of the season's most eagerly-awaited plays, not least because it is from the same team - producer Michael Redington, writer Waterhouse, O'Toole and director Ned Sherrin -who gave us the hit Jeffrey Bernard Is Unwell.

'We're the oldies and Tara's the newcomer,' says O'Toole. 'I said we should throw her in the deep end and we have. It's the only way to tell if someone can do it or not - and I tell you, Tara can do it.'

Tara, however, is not so sure.

'My chief fear is of the unknown, because this is my theatre debut. Not just in theWest End, but theatre, full stop. I trained at the Drama Centre in north London, but was hurled straight into film and television work.

' Of course, it helps if you've got a great story, and with Keith Waterhouse I've been so lucky. Angela, the girl I play, is known around wine bars in London as a general factotum who's also searching for love - and we can all identify with that.

'My scenes with Peter are very sexy but, just for once it doesn't involve me taking off all my clothes. The love scenes are playful and suggestive.

'Not that I would have minded performing nude. I don't share the anxiety people have in this country about sex. If you do a film in France and you're asked to strip, it's no big deal. No one bats an eyelid. If I feel secure with the director and the co-star, and I feel comfortable, I will go for it. There's no point doing something half-heartedly.

'The story in Our Song is told through Peter's character, Roger, an advertising executive, and each scene reveals a little more about Angela and their 16-month relationship. You're always left wanting to know more about her.

'We are all constantly trying to make the perfect matches and constantly coming unstuck. It's nothing to do with age, it's to do with us lot, us human beings.

'That's how Peter sums up the play, and he's right. We are always looking for the perfect partner,but sometimes it's easier just to get on with your work and wait for the right person to turn up.

'I've had boyfriends but I haven't had the love of my life yet. I'm a great romantic, but all in its own time, and I like it to work both ways.

'Often I buy whoever I'm going out with flowers. Or sometimes I forget the flowers and just invite them into the bath with a drink. It's a good way to relax.

'Of course, young people have a whole different attitude today. When I was 17 we were completely wild in that respect. You went to parties and people were snogging in wardrobes and things like that. Now people are very tame and adult. They're much more nervous about giving up something of themselves, and I'm sure it has a lot to do with AIDS. There's a new morality and we've all been stopped in our tracks because of it,' Tara says.

She puts much of her lack of inhibition down to her mother, photographer Sarah Fitzgerald. Indeed, while Tara searches for another apartment, she has returned to stay at the family home in south London, where her mother lives with Tara's stepfather, actor Norman Rodway.

'I'm very close to my mother because, for a while, we had only each other. My father died when I was 11, and we didn't have much money.'
Their lifestyle was eccentric, but happy: Tara's mother waitressed for a living and, to her more materialistic daughter's embarrassment, drove a succession of small, rusty cars.

'When you come from that kind of background, it does strengthen you,' says Tara.

'And I've always had to be practical, although I did have my wild days at my comprehensive school in south London. I wanted to do drama, but the teachers wouldn't let me, so I left.

'I was a waitress for ages, then I went travelling around Europe with a girlfriend. When I became 18, I felt it was time to go to drama school,' says Tara, whose great-aunt is the actress Geraldine Fitzgerald, who appeared with Laurence Olivier in the 1939 film version of Wuthering Heights.

'Just as I was about to leave drama school, I was offered Hear My Song. An agent, Caroline Dawson, came to see me in a production at the Drama Centre, and she has represented me ever since.'

Tara has enjoyed some of the luckiest breaks in showbusiness since that time. After Anglo-Saxon Attitudes came a part in the BBC's superbly-made film of Pirandello's Six Characters In Search Of An Author, which will be shown soon.

And there is talk of more films - perhaps even one for Hollywood - when she completes her run in Our Song next year.

'When we were doing Hear My Song, the director wanted a hint of Audrey Hepburn about me,' says Tara. 'My hair was pinned up and, for a moment, I felt like Audrey in Breakfast atTiffany's. It was the history and the glamour that rubbed off on me and I liked it.