The reason is Love Hurts, the painless BBC series in which she falls in and out of love with an engagingly wooden Adam Faith. The show is in its second season, and draws an audience of 8 million. This week Zoe Wanamaker returns to the theatre, and an audience of 500, playing a woman addicted to Valium in Arthur Miller's new play, The Last Yankee.
Unusually, the play has two premieres, one at the Manhattan Theatre Club, the other at the Young Vic. As the holder of a US passport, Wanamaker could have been in either, but she is in the London one. We meet in a dressing-room backstage, the day after the first preview. She greets me with a warm, firm handshake that dispels all thought of the nervous hand-wringer who gripped the preview audience. She takes the large red armchair, places her script, her tobacco pouch and liquorice Rizlas down by her feet, and beams.
She has 50 credits on the stage alone, including two awards - for Kattrin in Mother Courage and May Daniels in Once in a Lifetime - and eight nominations. She has been in an Arthur Miller before, and at the Young Vic before.
How had the preview been for her? 'I'm half-way there.' She has just been running lines with the cast. How will tonight differ? She attempts one answer, then another, then closes her eyes and turns her head from side to side. 'Acting is such a terribly odd thing to talk about. I find it really rather silly.' She laughs.
We discuss The Last Yankee, and she flicks to the back of her script, where she has pencilled some rehearsal notes: 'I wrote, 'Trying to hang on to reality in the face of the pressures in society, which are likely to force you to go under'. ' She closes the script. 'That's basically it.'
The challenge here was 'getting into the mind and body of someone who has been on Valium for 15 years'. The cast visited the Ealing Drug Advisory Service. 'One girl I saw did this all the time,' says Wanamaker, wringing her hands like a wet handkerchief, something she does in the play. 'And taking the sweat off her palms.' She scrubs her palms on her jeans. 'And her pockets were stuffed with tissues.' The thing is, she says, 'to make it real without making it a turn'. If she has a trademark, that is it.
Zoe Wanamaker was born in New York. Her parents lived in the country, in Connecticut; when she was three they moved to England. Her father, the actor, director and Globe Theatre campaigner Sam Wanamaker, was blacklisted during the McCarthy period. Her mother, Charlotte Holland, is a former actress. There are three daughters, Abby, Zoe in the middle, and Jessica. Does she have any memories of America? 'No. None at all. I can't remember what happened last week.' Does she feel American? 'Everyone asks me that.' Sorry. 'No. It's OK. I feel slightly alien in both countries.'
She grew up in Hampstead, went to a Quaker school, though she is Jewish, and studied painting before going to ballet school. Her parents didn't want her to act, but she's been doing so now for more than 20 years. Although she has had several long-term relationships, she has neither married nor had children.
When the run ends in March she will spend eight months filming the third series of Love Hurts, which includes location shooting in Tel Aviv. 'Then that'll be it.' She'll look for other parts. Charity executive, prostitute, countess's daughter, Valium addict: a typical Zoe Wanamaker character is atypical. The woman in The Last Yankee is one in a line of strong, idiosyncratic, damaged characters. 'I was never the ingenue,' she says, using her fingers as quote marks. When she played Emilia in Trevor Nunn's Othello, 'Trevor had me coming on with a dope pipe at the beginning of the second act.' As the prostitute married to the prime suspect in Prime Suspect, she displayed surly defiance shot through with lonely suspicion, and won a Bafta nomination.
There's a feline swish to her figure that matches the tough purr of her voice. The image does not go away as you take in her slow eyes, long, ski-jump nose and thin upper lip. Cheshire smile one moment, claws the next. The looks give her a grainy vulnerability, and mixed feelings. In another interview she said she had contemplated liposuction and collagen injections. When I raise the subject of looks, she groans, the only hiccup in a cheerful, brisk half-hour. 'You're not going to ask me this] Ugh. I said it once and . . .' She sighs. OK, let's move on then. 'Yes, let's move on. That's a boring one. Let's talk about the play.'
'The Last Yankee' (Young Vic, 071-928 6363) is reviewed by Irving Wardle in the main paper. 'Love Hurts' continues on BBC1 on Friday (9.30-10.10pm).