Here's a good question for the kind of quiz that surfaces in the papers at yuletide. Who is the only Chancellor of Stirling University to have appeared in a list of the century's sexiest women? All right, let's make it easier. Which Dame of the British Empire did the readers of Playboy recently rate among the 100 most winsome dames they could name? Very well, let's reverse the paradox. Which internationally renowned, still-youthful 60-year-old actress now makes a speciality of playing ageing ogres and what she herself calls "embittered old bags"?
The answer is, of course, Dame Diana Rigg. After Euripides's Medea came Brecht's Mother Courage, and after that human hyena came Martha in Albee's Who's Afraid of Virginia Woolf?, and after that raging dipsomaniac came Racine's Phedre and the same author's Agrippina, women turned into monsters by (respectively) lust and power. If she were to confide a determination to play Medusa, Caliban or the Cyclops, I think my eyebrows would stay unraised.
Rigg has spent much of the 1990s failing to dwindle into a silver- haired charmer, still less an old dear; and she is not finished yet. Remember the Mrs Danvers she played in a TV version of Daphne du Maurier's Rebecca, picking up an Emmy for her efforts? You can see the same mushroom-coloured face and much the same baleful stare on BBC2 over Christmas, when Rigg puts in a characteristically fierce, unfettered performance as a woman whose lifework is to ensure that her clan's blue blood remains untainted by anything fresh or new: Madame de Bellegarde in an adaptation of Henry James's The American.
Imagine the reaction of your average star if Paul Unwin, who directs, had offered her the role. Isn't the character offputtingly unsympathetic? Wouldn't it be bad for her image? But Rigg thinks that weird, difficult or evil characters are more rewarding to play, and that sympathy can only emerge unsought, unforced and of its own accord. Equally, she dismisses concern with image as "rubbish".
It isn't surprising, then, that she decided to play grim old Bellegarde after Unwin told her he wanted to renounce sentimentality and prettiness for emotional immediacy. "Costume dramas tend to be so bloodless it can be hard to pick one from another," she says. "It was when Paul said he was aiming for a robust, passionate style that I wanted to join the exercise."
It now seems odd that, less than a decade ago, Rigg would probably have been made a DBE mainly for her conscientious toil on Arts Council reports and the like. She had given fine performances in the 1960s and 1970s, but spent much of the 1980s bringing up her daughter. By 1991 she felt professionally abandoned: "I put my hand up and said adsum, and nobody wanted to know."
It was a call from Jonathan Kent, co-director of the then obscure Almeida, that changed everything. His production of All for Love, Dryden's version of Antony and Cleopatra, remade her career, and her Egyptian queen began to make the Islington theatre's reputation. There followed a series of once-potent characters darkly involved in the struggle to survive, most recently Nero's mother, Agrippina, in the Almeida's West End season: "She has really manoeuvred to get where she is, and now she feels it slipping away, so she has the terror of someone with her knuckles whitened on the last vestiges of her power. I suspect she knows what she's given birth to, and that he will kill her."
Would she count that her most satisfying role, then? Yes and no. "Always the particular one I'm doing is my favourite. I give it my total and utter loyalty at the time. I don't want to sound complacent, but I just love my work. I still feel a sense of relish whenever I go into the theatre at night, and I love it when I look up at the curtain-call and see all those spectral faces in the gods. I try not to see them as a body of people but as individuals, and I bless them every night."
Rigg is a conscientious preparer of roles. For Bellegarde she immersed herself in books about 19th-century Paris, although they were of limited use when she came to play a character so trapped in her aristocratic eyrie. But she also relies on observation, imagination and her immediate emotions. With Medea, the horror of children splattered to death against a wall was much in her mind. "And that scene in Virginia Woolf where Martha's husband destroys her I found very painful. I can't cry to order. I have to feel it then and there. But with Martha I was in tears every night."
But wouldn't it be a relief to tackle some non-grim, non-painful roles? Well, a TV series in which she plays a 1920s detective called Mrs Bradley is in the offing. Yet the theatrical producers no longer seem to see her as the charming, humorous actress she can be. "I'm longing to do a comedy, I'd like to do a farce. But I don't get offered affable parts. I seem to have got slightly typecast. It's weird."
It's doubly weird because the reason she has never had the career she deserves on the big screen is probably that the producers have mentally typecast her in a diametrically opposite way. They have dismissed her as the lightweight who played leather-clad pranks in The Avengers and, a bit later, married James Bond in On Her Majesty's Secret Service. "I'm just not offered serious parts. My film CV is virtually non-existent, so they say let's not bother. I'd love the chance - not to be a film star, I've no delusions that way, but to do good work."
It is very contradictory; but then contradiction seems to be the lot of a woman who is currently preparing her inaugural lecture as next year's Cameron Mackintosh Professor of Theatre at Oxford, waiting for her majestically horrible Bellegarde to hit our TV screens - and being relentlessly teased by friends for her Playboy billing as one of our era's top sexpots. Eminent dame though she is, she admits to being gratified by the last of these achievements: "Wouldn't you be? It's a hoot. The whole Phedre company was crying with laughter. I may play old boots, and I may look like a right old boot in The American. But who cares if I'm that sexy? It's lent a new spring to my step."