It was the ultimate power play between two women who ruled.

Mary was six days old when her father, King James V, died and she inherited the throne of Scotland. After spending her childhood in France, she married the French king and was quickly widowed. When she returned to Scotland, Elizabeth suggested Mary marry a British earl, Robert Dudley, from her inner circle. Elizabeth hoped to control Mary through the union and keep Mary from coming for her crown.

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“Early on, Elizabeth had a lot of paranoia and jealousy about Mary, and she was torn between that and her desire to connect with Mary,”Mary Queen of Scotsscreenplay writer Beau Willimon tells PEOPLE in this week’s issue.

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MARY QUEEN OF SCOTS

Because of the power at stake between Elizabeth and Mary, who considered each other “sisters” at various points, neither ever let down her guard completely. They only ever communicated via letters or through their councilmen.

“It’s a fluctuating relationship,” says historian John Guy, whose bookQueen of Scots: The True Life of Mary Stuart, served a historical reference for the movie. “But these politics are essentially the problem. Both of these women are relatively young: When Elizabeth becomes queen she is only 25. When Mary takes up her throne in Scotland, she’s just 18. They are both vulnerable. They are both having to find their place and establish their power in the face of this patriarchal, male-dominated society in which the men basically think that women have certain defined roles and should fit in.”

Ronan and Lowden (to her left) inMary Queen of Scots.Liam Daniel / Focus Features

MARY QUEEN OF SCOTS

Mary agreed to marry Robert Dudley (Joe Alwynin the film) on the condition that Elizabeth leave her the British monarchy. Elizabeth wouldn’t accept that deal, and Mary ended up saying “I do” in 1565 to Henry Stuart, Lord Darnley — her cousin who also had ties to the British throne.

The couple produced a male heir in 1566, thus strengthening Mary’s claim to the English crown and frustratingElizabeth.

“When Mary actually goes to produce an heir, to a lot of Elizabeth’s advisors, they were terribly worried that this heir would pose a threat to Elizabeth’s own crown,” Willimon says. “But Mary did offer to have Elizabeth be the godmother.”

And Elizabeth accepts the honor. “Elizabeth not only says yes, as in the film, but she also says, our relationship is so good at this point that I might actually look at again at my father’s will and at the whole succession to the English crown,” Guy reveals.

But that consideration began to go south when Mary’s marriage did. Henry (Jack Lowden) made a weak attempt to take her crown and eventually Mary’s advisors had him murdered in 1567. As the men around Mary continued to conspire for her power, she was eventually forced to abdicate the throne and a council ruled on her son James’ behalf until he was old enough to take the reins himself.

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Cecil persuaded Elizabeth that the Spanish Amada was coming for England and the queen must up security, and only then did Elizabeth sign off on Mary being executed. Mary was beheaded the next year.

“The film is a call to look deeper at the cost that these women paid for power,” director Joise Rourke says. “But also the hope that we can make power easier for women.”

Mary Queen of Scotshits theaters on Friday.

source: people.com