When the cast of a 5-star, sell out West End production rests on the flip of a Sterling coin, you know you’re about to watch something special.

Mary Stuart, the critically acclaimed show documenting the conflict between Elizabeth I and Mary Queen of Scots, closed at the Duke of York Theatre today after a hugely successful run.

Lia Williams and Juliet Stevenson play the queens, but which actress plays which queen is decided on the night, right before the play begins. The hugely talented actresses walk onto the stage, surrounded by the cast of the play, and a camera zooms in on the spinning coin. Who ever calls correctly plays Elizabeth, rushed offstage and marked apart with a black jacket covering her white shirt; the other actress plays the eponymous Mary Stuart, whose shoes and socks are removed as she is imprisoned: surrounded by the brick walls of the stage.

The reason why this duality of parts works so well is the similarity of the characters themselves. The Virgin Queen and the Queen of Scots are metaphorically and, thanks to the genius interpretation, literally two sides of the same coin. Although Mary is trapped in the jail underneath the palace, Elizabeth is similarly constrained by the crown itself, stripping her of any free will and forcing her to sign her so called sister’s death warrant.

In the climactic final scene, A transcendent Mary Stuart becomes a martyr, and her beheading is accented by the crashing down of another wall, leaving Elizabeth imprisoned in her own castle, trapped in the constraints of her straightjacket-like corsets and lead face paint.

Mary Stuart is an incredible experience,  defined by the immense talent of the two leading ladies, either of whom could end the night losing her head.