EXCLUSIVE: Helen Mirren Reveals the Surprising Secret to Her 18-Year Marriage, Shares What She Misses About Al

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Helen Mirren and husband Taylor Hackford have been together for nearly 30 years, and on Wednesday, the 70-year-old actress revealed the surprising secret to their long-lasting romance.

“Spending a lot of time apart,” Mirren told ET with a laugh.

The actress said that she and Hackford -- who tied the knot in 1997 -- do “miss each other terribly” when they are away, but added that it’s important they give each other “room to be who they want to be,” as well as supporting one another in their professional and personal lives.

“That has to be a two-way street,” she added. “I'm very lucky that Taylor gives the same to me, you know? It's a mutually-supportive relationship.”

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Mirren spoke to ET at a junket for her latest film, Eye in the Sky, a thriller which centers around the controversy of drone warfare. The actress revealed that, while she usually chooses projects based on the character she will play, in this case, it was the story that attracted her.

“The greater appeal was the totality of the film, the totality of the story, and the way in which it brings up all the complicated moral issues of war, and presents it, I think, in an extremely dramatic and truthful way,” she said. “I wanted to do the character the best I could to fulfill its function in the story, but really it was the story that I thought was really interesting.”

Eye in the Sky
is the latest Hollywood project to tackle the controversial topic, and Mirren hopes that it will leave viewers thinking about the moral implications of unmanned combat.

“In a way, it's sort of like a courtroom drama,” she said. “ We're presenting the evidence of a particular action, and it's being done in your name, you sitting out there in the audience. Do you think this is the right thing, or do you not?”

“It speaks well to our system, I believe, and it presents the argument, I think, very well,” she added. “It's very easy to have a knee jerk reaction in these situations. ‘Oh, that's terrible. You must never do that. Oh, that's appalling.’ It is appalling, but the alternative is maybe more appalling.”

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The film is also notable as it marks Alan Rickman’s final project, and audiences in the screening reacted audibly when the late British actor -- who died on Jan. 14 after a battle with cancer -- appeared onscreen. Unfortunately, Mirren had no scenes with the legendary actor, and the two shot their parts at different times, though the actress says she thinks Rickman would be “proud” to have Eye in the Sky as his final film.

“It speaks to his sense of morality and politics and engagement in our democratic values. He was very much that person, as well as obviously being the great actor we all know him as being,” she reflected. “There's huge outpouring of love for him in London, because we knew the other side of Alan. There wasn't just the sort of movie star, you know, actor side of him.”

Mirren also shared a sweet memory of Rickman when asked what she’ll miss most about the star.

“He was the best person to go out to dinner with,” she recalled. “He was very generous. He always insisted on paying the bill, he was just entertaining and fun and funny and loved going out to dinner and chatting. He loved that.”

Eye in the Sky
hits theaters March 11.

WATCH: Emma Thompson, Helen Mirren and Tim Allen Among Stars Paying Tribute to Alan Rickman