Helen Mirren may be one of Britain’s great acting dames, but the actress, born Helen Mironoff is actually half-Russian. “It’s my bottom half that’s Russian,” she joked to Newsweek. Mirren’s heritage was part of the reason she took on the role of Catherine the Great, one of Russia’s longest-reigning and most famous rulers, in the HBO series Catherine the Great, premiering Monday on HBO. The actress playing Catherine the Great happened almost by accident. At the world premiere of the series in London, Mirren said: “Usually the last question when you’re interviewed is what would you like to play, and my mind was blank at that moment until in my head I thought: ‘Catherine the Great would be an interesting character to play.’ I was rather cavalier, but [the makers of the show] were listening.”

As a result of Mirren’s public declaration, the Oscar-winning actress was invited to play the Russian empress in a four-part HBO drama. In researching the role, Mirren found herself falling in love with the character. She revealed to Newsweek how she got ready to play the legendary ruler, saying: “You have to you have to do your research and you have to look into their eyes and understand. “I was very fortunate with Catherine because her letters exist—many, many letters. She was a prodigious writer and a wonderful writer, very accessible, funny and smart.” In these letters, Catherine wrote frankly about her lovers and affairs in a way that Mirren admitted she found shocking. “I have been through the liberal revolution, the sexual revolution, the ’60s and the rest of it, but actually in reality we are still coming out of a kind of Victorianism, a Protestant Puritanism. We still do have certain inbuilt attitudes,” said Mirren.

“Even though I think of myself as a liberated woman, I still couldn’t get my head around her sexual liberation until I thought, ‘You just have to think like a man. Men don’t have a problem with this. You have to think like a man, or a king or a tsar.'” According to the actress, Catherine’s sex life was just a wider part of her hunger for power. “She wanted power, and she was not about to share it with anyone. She knew the danger of marriage early on.” Catherine’s marriage to King Peter III of Russia ended with her wrenching power from him as part of a military coup; a coup that ended with him dead at the hands of some of her closest allies when Peter was strangled with a scarf after a night of drinking.

Mirren said that another key to understanding Catherine was to consider her role in the coup, which happens just before the events of Catherine the Great. Though her allies had put her on the throne with the idea that she would work as a puppet ruler for them, “they absolutely misjudged her, imagining that she would, like a nice, quiet little girl, back off and allow them to rule.” When asked what she learned from playing the character, Mirren said: “That women, if they have the capability, can do anything, absolutely anything if they have the ability to work hard. Because that’s a defining quality of Catherine, her ability to work incredibly hard. If women have the capability and the ability to work hard they can do anything, including becoming the Empress of Russia.”

Catherine the Great airs Mondays on HBO.