I would love to have been a fly on the wall when Dame Helen Mirren strode into the whorehouse. At first she didn’t want to go, but Taylor Hackford, the director of her new film, Love Ranch, insisted they spend a night there. The fact that Hackford is also Mirren’s husband didn’t make it any easier.

“I knew she needed to do it for her research,” Hackford said in a phone interview last week. Love Ranch (which opened in theatres this week) is based on the true story of the Mustang Ranch outside Reno, Nev., which in 1971 became the first legal whorehouse in the United States. Mirren and Joe Pesci play Grace and Charlie Bontempo, fictionalized versions of the proprietors at that time, Sally and Joe Conforte. “I said, ‘Listen, I’ve watched you prepare for every role of your life,’ ” Hackford told Mirren. ” ‘When you were doing [the TV series] Prime Suspect, you went to Scotland Yard. Why should this be any different?’ ” “I remember I took a book with me,” Mirren said, also in a phone interview. “I thought, ‘Maybe I’ll just find a little corner to hide in.’ ” There are mighty roles for men in Shakespeare, but for a grown-up actress, there are very few. As if. Within minutes Mirren had bonded with the working girls, who told her their stories and performed one of their famous lineups for clients. “I lost her. She just took off,” Hackford said, laughing. “Helen loves women, and she’s interested in women’s societies. About 5 in the morning I finally said, ‘Hey, we’ve got to get out of here, we’ve been here since 8 p.m.’ She was having a ball.”

“Luckily it wasn’t a busy night,” Mirren said. “I don’t know if I could have handled that. There was one unbelievably drunken guy who could hardly stand up. He was being very sweetly guided around. One of the girls eventually said, ‘Come on, baby, you’re with me.’ I loved being there. It’s quite an extraordinary and very specific environment, and it was invaluable that I should experience that.” That’s the great thing about Mirren: In addition to being a brilliant actress, fiercely intelligent and regal as hell, she also seems fantastically game. In conversation she’s warm, she listens, she laughs a lot. Even over the phone, she crackles. Now 64, she’s pulled off some exceptional feats: She’s one of the sexiest women on Earth, lusted after by men of all ages. Yet not only is she not threatening to women, she’s adored by them. In an industry where actresses tend to disappear at 40 and emerge 20 years later as grandmas, she’s doing some of her most exciting work: She won an Oscar for The Queen (2007) and nominations for The Last Station (2010), Gosford Park (2001) and The Madness of King George (1994). She took home Emmys for Prime Suspect (2006, 1995) and Elizabeth I (2005), and numerous awards for her stage career. And she’s become more beloved the older she gets, which, for an actress, puts her and Meryl Streep in a rarefied club of two.

She’s got a list of coming projects as long as a thigh bone, an apt simile because they all look pretty kick-ass: She’s a former Mossad agent on a revived mission to capture a Nazi war criminal in The Debt. She stars opposite Bruce Willis in Red, an action-comedy about black-ops agents. In the remake of Arthur, she’s taking over the butler role that won John Gielgud an Oscar in 1982 (Russell Brand plays her spoiled employer). And in The Tempest, adapted and directed by Julie Taymore, she performs a sex change on one of Shakespeare’s most titanic roles, turning Prospero into Prospera. “There are mighty roles for men in Shakespeare, but for a grown-up actress, there are very few,” Mirren said. “I’ve done Cleopatra, that’s about it. Lady Macbeth, but that’s not a great role, actually. So I was at the theatre seeing The Tempest for probably the fifth time, and I suddenly thought, ‘This part could be played by a woman.’ ” Soon after, she met Taymore, and two years later they were shooting.

“I don’t think it’s a particularly male role at all,” she said. “I think it fits much better on a woman. One of Prospero’s most famous speeches, the Ye Elves speech, is lifted almost word for word from a woman’s speech in Medea. And the relationships with Miranda, Caliban, Ariel, they all becomes matriarchal.” Mirren insists, however, that she’s not seeking to dominate the screen any more. “No, no, I feel the opposite,” she said. “The smaller the role, the better, as long as it’s fun, and pro-active. I feel I’ve done the other, really. It’s hard work.” She laughed. “I just don’t want to play people who are dying. As you get older, you get asked to play people who are dying all the time.” Hackford’s career, on the other hand, has had its ups and downs: He made An Officer and a Gentleman and Ray, and is currently president of the Directors Guild of America, yet Love Ranch’s budget, $18.5-million (U.S.), is the smallest he’s ever had. But Mirren’s greater fame “isn’t hard on my ego at all,” he said. “One, I deeply love her and enjoy being with her, and it’s continually exciting. Two, when I first met Helen [he directed her in 1985’s White Nights]and brought her to Hollywood, she was ignored. To see your wife continuing to rise because of the quality of her work, we all aspire to that. It’s taken the world a long time to discover her, but she did it her way and I’m thrilled.”

He sure gave her a humdinger of a sex scene in Love Ranch. Grace falls for an Argentine boxer (played by Sergio Peris-Mencheta) whom Charlie sponsors. When they get naked, it’s shockingly unadorned – no gelled lenses, no soft lighting, nada. “Helen always says, ‘I’m going to let the inner light shine,’ ” Hackford said. “I think the audience, especially the women, really appreciate that.” “Yes, I am sort of hanging out there,” Mirren agreed, laughing. “Trust my husband to do that to me. But it’s his vision. He wanted it to be harsh, realistic. He’s not a romanticist, my husband, which I love about him.” They live in an elegant manse in the Hollywood Hills with family nearby (Hackford has two children, and Mirren’s nephew is a show runner on Criminal Minds), and try to stay above the fray.

“I am surprised to find myself here,” Mirren said. “You meander along this path of life, a step here and a step there, you go off the rails, then oh, you’re back on the path again. I don’t quite understand how I got to this very good place. It doesn’t mean there aren’t heartaches and angsts and all the rest of it, days when you’re full of insecurity. But you get through those, and on you go. But I am incredibly lucky, I must say.” So are we.