Over a nearly 40-year career in theater and film, Helen Mirren has managed a tricky balance: to be almost equally well known for her talent and for her willingness to get naked. She’s been a serious sexpot from “Caligula” (1979) through “The Cook, the Thief, His Wife and Her Lover” (1989) to last year’s “Calendar Girls.”

But the role that has cemented her fame is a grim piece of business: the relentless Jane Tennison, hunting down killers in the “Prime Suspect” television movies. The latest installment, “Prime Suspect 6: The Last Witness,” will be shown on PBS next Sunday and April 25 as part of “Masterpiece Theater.” Now a Detective Superintendent, Tennison is investigating the torture and murder of a Bosnian Muslim woman in London.

Ms. Mirren, 58, is married to the American director Taylor Hackford, and they split their time between Los Angeles and London. On a recent visit to New York, she took off her shoes and curled up on a couch in her hotel suite to talk with Ted Loos.

TED LOOS How do you think Tennison has changed since the first “Prime Suspect” in 1990?

HELEN MIRREN She’s gotten older, along with me. But TV characters are not real people, I’m sorry to disappoint you! People tend to think that these characters are actually real. It’s like asking: “How’s your Aunt Jane doing? I hear she has a problem with alcohol.”

LOOS There was a big gap between the last “Prime Suspect” and this one. Was it getting stale?

MIRREN No. I felt I was getting too identified with it. To be a success on television really sticks to you like glue. So I stepped away from it, thinking I would probably never do it again. But every year for six years, they came back to me and said, “We would like you to do it.” Finally I thought I had put enough distance between me and it.

LOOS At the beginning of “Prime Suspect 6,” Tennison’s bosses are hinting that she should take early retirement. Has anyone ever told you that you were too old for a part?

MIRREN They don’t say it to your face.

LOOS Would you ever take early retirement from acting?

MIRREN I’ve been working nonstop for two years, so it would be nice to take a break. But then something comes along and you realize why you do it — because you’re good at it. It’s the same for Tennison.

LOOS You’ve said you’ve never had plastic surgery or used botox. Is that still the case?

MIRREN Yes.

LOOS Would you ever?

MIRREN Yeah. People are looking at you on the screen. They’ve got to want to like you. It’s not just vanity. It’s the No. 1 tool of your trade — the close-up. I think people should have nose jobs. If a nose is ridiculous, it’s a distraction.

LOOS You’ve been nude on camera many times — it’s sort of a signature for you. Have you ever said no?

MIRREN Often. I did for this “Prime Suspect.”

LOOS What did they want you to show?

MIRREN They never say “large close-up on right buttock.” But I felt the sex scene they wanted was arbitrary. In other pieces, I’ve tried to add sex. I had read in Ayn Rand’s biography of this amazing moment when she appears at this man’s door naked except for a fur coat. When I played her [in “The Passion of Ayn Rand” in 1999], I said, “I think we’ve got to see it.” It was about character, because she was highly sexual.

LOOS Is there a difference between the nudity you do and Janet Jackson baring her breast at the Super Bowl?

MIRREN One very fake breast.

LOOS Is it all just fair game for entertainment?

MIRREN No. I think Jackson was sort of inappropriate. But people who have fake breasts have an absolutely burning desire to have people look at them.

LOOS Speaking of bodies on film, can you ever live down being a part of “Caligula”?

MIRREN I’ve never opened my mouth to denigrate “Caligula.” I was pretty young when I made that — not physically young as much as inexperienced in film. And you know what? It was a great experience. It was like being sent down to Dante’s Inferno in many ways.

LOOS What’s your enduring memory of that bizarre production?

MIRREN The first night I arrived on the huge set outside of Rome. They were shooting the big orgy scene with Peter O’Toole. So I’m taken to Peter’s trailer to be introduced. But he’s wrapped in his costume — bandages that were oozing with fake sores, pus and blood. I went outside and I threw up in a field.

LOOS Since you’re also a Shakespeare veteran, do you think you could give Martha Stewart’s story some of the gravitas you’ve given to Lady Macbeth?

MIRREN I don’t understand the vilification of Martha Stewart. She doesn’t deserve Lady Macbeth. In a way, she’s more like Rosalind from “As You Like It.” She’s mouthy, pushy and opinionated — kind of wonderful and kind of difficult.

LOOS You’ve played Rosalind. Would you like to play Martha?

MIRREN Absolutely. She must have amazing energy.

LOOS Can you get better restaurant reservations since Prince Charles made you a Dame last year?

MIRREN I haven’t used that yet and I doubt whether I ever will. I’d feel really tacky.

LOOS How did you feel about being asked?

MIRREN In England, it’s a big deal. I do feel it’s a great honor. But I had to think about it quite seriously for a couple of weeks. It does sort of squish you into the establishment thing. In the end my baser feelings got the better of me. I succumbed to pride.

LOOS Why have you not worked with your husband since meeting him on the set of “White Nights”?

MIRREN The films he wanted to do didn’t really have parts that I would consider. We’re trying to set up something now. He wants to do it. I think he feels guilty.

LOOS There’s a group known as the Helen Mirren Appreciation Society, and you’ve invited them backstage a few times. Don’t ardent fans scare you a bit?

MIRREN No. Because I think they’re great people. They’re very un-pushy. If I’m doing theater, they’ll all come at the same time. I feel like I absolutely have to say, “Thank you for coming.” I appreciate them as much as they appreciate me.

LOOS One of the British reviews of this “Prime Suspect” referred to you as a “goddess.” Can you be praised too much?

MIRREN It’s impossible. That’s the terrible thing about reviews — they’re never good enough. The bad reviews lodge in your heart like a poisoned arrow.

LOOS Is there one that still stings?

MIRREN I received an awful dart for my first big role, in “Troilus and Cressida.” I remember the reviewer: Benedict Nightingale. I’ll never forget him.

LOOS And he’s still out there writing, correct?

MIRREN Still out there, the bastard.