Keira Knightley has babies on the brain. One baby, in particular -- fellow Brits Prince William and Kate Middleton's little boy- or girl-to-be.

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Appearing on the March cover of Marie Claire, the 27-year-old actress -- who wouldn't make a bad Duchess of Cambridge in a screen adaptation -- says she's unabashedly thrilled about the upcoming birth of Britain's future monarch. She's less enthusiastic, however, about the system of monarchy itself.

"I'm over the moon about the royal baby," she gushes to the magazine. "But I really can't mount an argument in favor of the monarchy. Is that treason? Do I have to turn in my passport?"

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The Anna Karenina star has always been an independent thinker. And she gravitates toward other independent thinkers, too. Speaking about her fiance, Klaxons keyboardist James Righton, she notes that what makes them so compatible isn't their similarities but their differences.

"I get wonderful perspective by being with someone who is less like me than more like me," she tells Marie Claire of her husband-to-be. "The way he thinks is something I don't get. We come at things from totally different angles."

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One thing the lovebirds agree on? That their wedding -- whenever it happens -- will be simple.

"I could have six fake weddings. God, that would be expensive," jokes the typically private, low-key star. "We're not really big wedding types. I don't need to have all that."

This article originally appeared on Keira Knightley on Kate Middleton's Pregnancy: "I'm Over the Moon"