The actress plays Tudor monarch Queen Elizabeth I in the historical drama, sharing the screen with Saoirse Ronan who plays the titular character. For her work on the film, Margot has been nominated for a Screen Actors Guild Award in the Outstanding Performance by a Female Actor in a Supporting Role category, but surprisingly, she initially didn't believe she was right for the part.
"To begin with I'd said to Josie (Rourke, director), 'I'm not the right actress for this'," the "I, Tonya" star recalled in an interview with BBC News. "I didn't go university, I don't have a degree, I didn't do theatre, I'm not classically trained, I learned on the job. I really think I'm the wrong kind of actress for this. I'm the wrong kind of actress to play a queen."
However, her concerns were soon alleviated once Josie explained what she wanted Margot to bring to the regal role.
"She said, 'I don't want you to play a queen, I want you to play a young woman'," Margot smiled. "And that unlocked the character for me in a big way, and from then it was really finding her humanity and finding the vulnerability beneath the facade, which made the facade all the more tragic to me to be honest."
The Oscar-nominee also got a confidence boost knowing that Saoirse would be one of her fellow cast members.
"I've wanted to work with Saoirse forever anyway, and I hope we get to again," she told MailOnline during the film's London premiere. "She's just incredible and to know she's at the helm of this film just feels me with confidence. She makes such good choices."