WHEN actress Zoe Tapper walked into London's College Of Psychic Studies a year ago to speak with a spirit medium she was cynical about what she was going to hear. Who wouldn't be? "I didn't give anything away," says the 27-year-old Londoner, curling up on a sofa in the British Film Institute bar and sipping a glass of water. "I dressed very neutrally, decided I wasn't going to speak very much and actually came away thinking that it was a pile of old claptrap. What I was told was very generic. I felt it could have been about anyone."

The visit had more of the character of a field study than a desire to contact "the other side", however. Tapper was researching her upcoming role as Victorian spirit medium Selina Dawes in Andrew Davies's blockbuster adaptation of Sarah Waters's novel Affinity. Every festive season needs a ghost story and Affinity is this year's offering from ITV: a sumptuous period piece filmed in Romania and also featuring Amanda Plummer, Anna Madeley and Bleak House's Anne Reid.

So far, so rational. But joining Tapper on her visit to the College Of Psychic Studies was Affinity director Tim Fywell. His experience with a second medium was entirely different. "He was very shaken by it," Tapper recalls. "We went for a coffee afterwards and he told me a few things. He was visibly shocked at what he had heard and experienced. I was immediately intrigued and thought, I've got to go and see this woman'."

So she also visited medium number two. And, like Fywell, she heard things nobody could have know: detailed facts about her family and about past events in her life. "What was different about her was she talked in specifics," explains Tapper. "She said almost immediately, You're a worrier but there's this place you should go, a place where you can rest and relax'. I said, Where is it?' and she said, It's a chalet in Switzerland'. Well, my fiance is half-Swiss and his family do have a chalet in Switzerland. I've been a couple of times and love it there."

Was she convinced, then? Not entirely. But she was intrigued enough to base the character of Selina in part on the woman. Selina is behind bars when we first meet her, having been jailed as a fraudulent medium. As her friendship with high-born prison visitor Margaret (Anna Madeley) develops into something a little more passionate, her story is told in flashback. It's a tale involving supernatural happenings, ghostly apparitions, a séance or two and a malevolent spirit called Peter Quick. So is Selina actually what she claims to be? Margaret certainly thinks so.

Affinity is the third Waters novel to be filmed, and the first by ITV. To date the BBC has screened adaptations of Tipping The Velvet, in 2002, and the Booker Prize-nominated Fingersmith, in 2005.

As with the other novels, Affinity has a Victorian setting and a strong lesbian storyline though unlike the now-infamous Tipping The Velvet - also adapted by Andrew Davies - there isn't a strap-on leather dildo in sight. Affinity is a story about the repression of desire rather than its expression. "People do jump onto the lesbian side of things," Tapper sighs. "Because of the success of Tipping The Velvet, which was very raunchy and quite explicit, people assume that's what Sarah Waters writes about. But in Affinity it's not about sex, even though there is a lesbian relationship, it's about the women's spirituality, and about their repression."

Given their focus, the novels do necessarily feature strong female characters. That makes their small-screen adaptations a gift for actresses. Keeley Hawes and Rachael Stirling starred in Tipping The Velvet and Hawes graduated from there to lead roles in high profile shows like Spooks and Ashes To Ashes. Fingersmith put Elaine Cassidy and Sally Hawkins in the spotlight and Tapper is well aware that she and co-star Anna Madeley have been blessed with a similar opportunity.

"I'm shocked at the imbalance between the good roles for men and good roles for women," she says. "I don't want to climb on my feminist bandwagon too much but it's rare that you get a script which is about the relationship between the women and not just about them as sexual objects. When I read this script I was overjoyed to see a character who was so complex and had such depths to her. You just don't come across them that often."

In fact, Zoe Tapper doesn't need a spirit medium to tell her she has a bright future. As well as Affinity, she can currently be seen in the BBC's remake of cult 1970s series Survivors and in the New Year she stars in Demons on ITV.

Demons is a ludicrous, though highly enjoyable, six-part fantasy romp which takes elements of Bram Stoker's Dracula, updates it to 21st-century London and chucks in Philip Glenister, Richard Wilson and Mackenzie Crook. Imagine Life On Mars's Gene Hunt as a wisecracking American vampire "smiter" walking through the set of Hellboy with the cast from Buffy and you have an idea of what awaits.

Tapper plays Mina Harker. The character features in Stoker's original novel but in the hands of the Demons scriptwriters she has been turned into a blind concert pianist living in modern-day London. "We were filming for four months and I got very used to not looking people in the eye," she says.

Several scenes were filmed in the brutalist folds of the South Bank complex we are sitting in now. Today there are only a few skateboarders rolling around its grafitti-daubed cracks but in the world of Demons you are more likely to encounter fictional nasties, people like Redlip, Pyromancer or the devilish Gladiolus Thrip, played with relish by Mackenzie Crook.

Demons also re-unites Tapper with the producers of Hex, the fantasy series broadcast on Sky which has proved such an extraordinary nursery for British-based acting talent. As well as Tapper it featured Michael Fassbender, star of the Camera d'Or-winning film Hunger and seen most recently in The Devil's Whore, and the Lost In Austen pair Jemima Rooper and Christina Cole.

But if Hex was Tapper's introduction to the viewing public it wasn't actually her first role: just days after leaving London's Central School of Drama she started work on Stage Beauty, Richard Eyre's 2004 film about Restoration London. Tapper plays Charles II's mistress Nell Gwynn and her co-stars included Rupert Everett, Clare Danes and Billy Crudup.

"I was so green. I literally started the Monday after finishing drama school," she laughs. "Everything excited me. I remember walking into the changing room and seeing a bowl of fruit and thinking that was just the most glamorous thing. I even rang my mum and told her."

But, she adds: "There was an arrogance attached to the way I got the job. I wrote to the casting director saying: I am Nell Gwynn. You must cast me in your film. You'd be mad not to'. God, I'd never do that now."

She followed Stage Beauty and Hex with a leading role in the well-received BBC adaptation of Patrick Hamilton's 1930s trilogy 20,000 Streets Under The Sky. She also appeared alongside Steve Coogan in The Private Life Of Samual Pepys and acted with Joan Plowright in the 2005 film Mrs Palfrey At The Claremont.

To date, prostitutes and aspiring actresses have been her stock-in-trade, though she is now adding clairvoyants and vampire smiters to the CV. None of those professions figured large in her unremarkeable suburban childhood.

Zoe Tapper was born in Bromley in Kent in 1981. She has one brother and her father worked first as a wine buyer for Sainsbury's and later as an advisor to the National Farmers Union. Tapper acted in all the school plays going but the only connection with the theatre were the neighbours who dabbled in amateur dramatics.

"Acting wasn't something I realised I could do as a career. I don't come from a family which has any links with acting. I was all set to go to university and study English," she says. "In another life I would have done that but somewhere in the back of my mind I knew I wanted to act. As soon as I realised I could go to drama school, that that was a viable option, I deferred my university entry for a year and auditioned for drama school."

Her parents were supportive but it was her mother, the vice-principal of a further education college, who gave her the best advice. "When I eventually made the choice not to go to university I remember my mum telling me, The thing to do is never have a Plan B. If you have a Plan B you'll end up falling back on it'."

I like the sound of Zoe Tapper's mum, a Grimsby girl made good. Tapper tells me another story about the time she herself volunteered to work with the Crisis Christmas organisation, a charity which opens drop-in centres for the homeless and vulnerable during Christmas week. One of her fellow volunteers was a boy her mother had taught, one of the "naughty kids" who were always on the verge of expulsion. "I used to know an Yvonne Tapper," he said, peering at Tapper's name badge.

"That's my mum," she replied.

She then heard how her mother had called the boy into her office, told him he was heading for expulsion but that she believed in second chances and was giving him one now.

"He turned himself around and went on to university. He said she really inspired him and that was why he was doing this volunteering, to give something back. At that moment I couldn't have felt more proud of my mother."

Tapper will be busy again this Christmas, though it's her forthcoming wedding that's occupying her time now. On December 30 she marries fellow actor Oliver Dimsdale, he of half-Swiss Alpine chalet fame. Dimsdale played Louis Trevelyan in the BBC's 2004 costume drama He Knew He Was Right, and runs his own theatre company, Filter Theatre. The honeymoon will be in the Far East: in Cambodia, for the temples, and Malaysia, for the tan.

She'll return to find herself in the same position she left from: sitting on the cusp of fame, one of those actresses whose name you recognise even if the person isn't always so easy to picture. Channel surf over the Christmas period and you'll see her with cropped blonde hair (Affinity), long chestnut hair (Survivors) and coiled black hair (Demons).

Tapper says even the make-up artist for the Sunday Herald photo shoot admitted she had found three different internet images of the actress and thought she was looking at three different women. "I thought, God that's fantastic'," she laughs.

The face, though, is unmistakeable. It's the moles you see, one below the nose, the other at the corner of her mouth. We can expect to see a lot more of them - and her - in 2009, though Tapper is sanguine about the prospects of more parts like Selina Dawes.

"It's a product of the current climate," she says. "Even my experience of the audition process tells me that people are scared of getting it wrong these days. You're only as good as your last job and that goes through the whole industry. Certainly when I started out you'd get the job if the director liked you. Now you get a call from your agent saying, Well they're 80% sure' but then it has to go to the financiers and 10 different executive producers. I do worry that's diluting drama because people don't seem to be taking quite so many risks.

She may talk like an old hand but, refreshingly, there is still plenty of the ingenue about Zoe Tapper. "Oooh, make sure you watch Survivors tomorrow night," she says excitedly at one point. "It's my big episode!". Five years into her career, though, she has already crammed in more than some actresses manage in a lifetime. You can count them off for yourself: classy British films, peerless television adaptations of classic novels, prime-time telly and a cult niche series that looks increasingly like a who's who of the next generation of British acting talent.

She has even acted opposite a genuine Hollywood legend, sharing screen time with Lauren Bacall in Julia Taylor-Stanley's 2006 film These Foolish Things. Bacall plays a grand-dame of the theatre, Tapper the young wannabe. In one scene, Bacall comes up behind Tapper in her dressing room as she's about to go onstage, puts her hands on her shoulders and whispers words of encouragement in her ear. Tapper's eyes glisten as she relates the story.

"She says I'd give anything to be where you are now' and I say Where's that?' and she says At the beginning'. I got a chill when she said it but after the shot she turned round and said It's absolutely true. I would give anything to be there now.' I'll never forget it." And she beams at the memory.

Affinity is on ITV on December 28 (9pm). Survivors concludes on Tuesday on BBC1 (9pm). Demons starts in the New Year on ITV.