Sex is never far from the radar where Helen Mirren is concerned. Type her name into an internet search facility and the following message appears before your eyes: “You have entered a term which is likely to return content of a sexual nature, which may be inappropriate for children and offensive to some adults.” No surprises there, then.

In many respects, it could be the story of her life that even at 58, the recently-anointed Dame Helen should continue to command attention from the Loaded generation when she is older than the majority of the readers’ mothers. And Mirren was in the news again last week, promoting her role in the new British film Calendar Girls, a comedy-drama inspired by 11 members of the Rylstone and District Women’s Institute, who stripped for a fund-raising calendar in 1999, after the husband of one died of leukaemia. The cynics might retort that it would constitute a greater scoop if Mirren actually kept her clothes on for the duration of a movie, but the lady herself has no problems with disrobing. “This film is loving to women, and there was a huge amount of mutual support amongst the cast, so I am delighted with the way it has turned out,” she confirmed at Wednesday’s premiere in Leeds.

Sitting alongside Julie Walters, another stalwart of these occasions, Mirren seemed every inch to be central casting’s personification of the WI: quintessentially British, uncompromisingly plain-speaking, and an organisation quite prepared to boo the Prime Minister if the circumstances demanded it. Yet, the paradoxical aspect of her image is that she is exactly the opposite from Jane Wilson, the steely, taciturn individual she portrayed, whilst garnering an Oscar nomination for her work, in Gosford Park, a universe removed from DCI Jane Tennison, the heroine of Prime Suspect (which returns this autumn), and there is probably more chance of Madonna winning an Academy Award than of Mirren ever giving talks on jam-making and sewing.

Indeed, behind the scenes, and whilst careful not to upset her middle-aged sisters, whose fund-raising efforts have earned them star status on either side of the Atlantic, Mirren has admitted to being the very antithesis of their traditional membership. This may explain why contradictions abound in her character. It also defines why Mirren had proved so adept at slipping into a rich variety of guises, gowns and grotesqueries. Mirren is half-Russian. Her father Vasily-Petrov Mironoff came from a Czarist military family near St Petersburg, and her great-great-grandfather is mentioned in Tolstoy’s epic War and Peace. But Mirren grew up in England and her mother is English. The family’s name was changed to Mirren when she was 10.

She left St Bernard’s Convent School in Westcliff-on-Sea and, in defiance of her parents’ wishes that she become a teacher, joined the National Youth Theatre. The 18-year-old was quickly spotted by the Royal Shakespeare Company and rapidly became the “sex queen of Stratford”. Not a conventional beauty, and therefore blessed with more longevity (allied to talent) than the majority of her peers, Mirren has subsequently been revealing in both senses, taking her clothes off in her first film, Age of Consent, opposite James Mason, continuing the trend in the Penthouse-financed calamity, Caligula, a decade later, and maintaining her penchant for naturism in Peter Greenaway’s The Cook, The Thief, His Wife and Her Lover in 1989.

Rather like Honor Blackman, Susannah York and any fine wine, Dame Helen has improved, ripened, and blossomed with age. No longer is she the “depressed and f***ed-up” ingnue who used to cry herself to sleep every night at the RSC. Instead, she has gradually assumed an iconic reputation as somebody entirely at ease with herself, her body, her strong socialist beliefs and to hell what her detractors think. During her induction to acting, she carved a famous tattoo into the cleft of her hand: a crossed “V”, chiselled in American Navajo country, the symbol of eternal life and her career path was forecast with rare prescience by an American palm-reader, who studied her hand and predicted: “The height of your success won’t happen until you are in your late forties.”

Yet, as the mention of these trips into Stateside backwater locations may indicate, Mirren isn’t your typical luvvie, sipping Moet on the 19th floor of the Hyatt Regency, whilst emoting for their art and complaining about the slowness of room service. When Mirren talks politics, she does so with the passion which saw her endorse and then denounce Tony Blair, whilst her reaction to the 9/11 atrocities was straight from the Blitz. “We wondered what to do, then decided to carry on – because that was the best way of saying f*** you to the fundamentalists.” But whether it be campaigning for Oxfam, or raging against the small arms trade, one can detect the Russian blood in her roots, which bridles at people being locked into straitjackets of oppression. “One of the biggest causes of the underlying misery in the world today is the unstoppable availability to almost any group of a flow of guns from Britain, France, China, or wherever,” says Mirren. “The people are hungry, the NGOs get the food, but they can’t deliver it because of people with guns. How many times have we heard that refrain in the last few years?”

Given her intelligence, and her commitment to these opinions, it clearly bridles with Mirren that the adjectives “sexy”, “sultry” and “smouldering” are habitually attached to her name as if she was some addlebrained airhead, yet privately she acknowledges that nothing she says now will transform that impression. Indeed, recently, Mirren topped the Daily Mirror’s “Nudist League”, ahead of the usual suspects, J-Lo, Christina Aguilera and Kylie Minogue, and almost as if to confirm the stereotype, it emerged she has just finished filming an onscreen affair with Kylie’s current beau, Olivier Martinez, in The Roman Spring of Mrs Stone, a TV movie based on a Tennessee Williams novella.

Hence the slightly weary nature of her defence mechanism to inquiries about her looks, invariably prefaced with the reminder that she is happily married to American film director Taylor Hackford – so why on earth can’t people, and especially the media, differentiate between the actress and the real human being. “I just try to keep in shape, and do my best, and occasionally I do exercises, but mostly I don’t, and I am permanently on a diet, but I never lose any weight, so the fact is that I’m like anybody else. “I seriously thought a lot of this nonsense would go away when I appeared in Prime Suspect (where she locked horns with a brigade of chauvinist coppers, headed by the cuttingly snide Tom Bell), because that programme allowed me to step into who I actually thought I was as an actress. Because often, you’re cast in things and the directors are thinking of you as you were five or 10 years earlier. They don’t realise that you’re in your 40s, not 35 or 28 any more, and that you are entitled to regard yourself as a grown-up older woman, not some piece of eye candy. That’s why Prime Suspect was such a huge, stonking-great leading role at the time and a blessing for me. ”

As to the prospects for the comeback of this once-compelling police series, which seemed to have outstayed its welcome even before finishing in 1997, Mirren is cautious and defensive and prefers to focus on Calendar Girls, which may do for nude grannies what The Full Monty did for naked beer-guzzlers. After all, on the basis that the British love their Honors, Helens and Diana Riggs to strut their poses as don’t-mess-with-me dominatrices, the time is surely perfect, at the end of a summer of discontent, for a fresh slice of Ealing-style whimsy, with a touch of sauce flung in for good measure.

“My only fear was that in the wrong hands, it could have been rather mundane, middle-class, middle-aged, middle-England, middle everything,” says Mirren. “It could have been pretty bland and I was more nervous of that than any nudity or controversy. But I reckoned without the director, Nigel Coles, and the writer, Tim Firth, who did a fantastic rewrite from the first script I read. I’m convinced the result is a delight, even though I was left wondering how somebody like my character [Tricia] could pour all this tremendous energy into baking cakes and going in for ridiculous WI competitions when she could have been the head of a major industrial company.”

Maybe, ultimately, Mirren has suffered purely as a consequence of her gender. Harrison Ford, in his 60s, is still creating effortlessly junk-infested action flicks. Ditto Richard Gere. Dame Helen, by contrast, patently wants to escape the enervating “Phwoar” factor, but still finds the 1960s being dredged up and flung in her face. “I’m very very grateful to have met Taylor. And I have a feeling of being not owned but possessed, which I haven’t experienced before,” says Mirren, whose affection for her film-making partner, stretching back to 1985, didn’t prompt her into broody thoughts. “I was never drawn to babies and my skin still crawls when I see a little girl hauling around a great big baby doll. Basically, I don’t think I would have coped too well with being a mother and it wasn’t for me. But I recognise that as your body gets older, your mind gets better and you learn to deal with relationships. Above all, if I’ve learned anything, it’s that to be obsessed with your looks is utterly pathetic. It’s just not important.”

As the curtain lifts on Calendar Girls, Helen Mirren’s advice is understandable and even timely, considering the pressures imposed on teenage girls to resemble stick insects. The saddest aspect is that it probably won’t matter a jot. Come 2005, we can expect her to receive a swinging 60s revival.