When two actors alternate in a pair of lead roles, the performance often starts with a ritual to decide who’s who. For the RSC’s Doctor Faustus a while back, it was whose match burnt longest; for Robert Icke’s revival of Schiller’s Mary Stuart, it’s the spin of a coin. Juliet Stevenson and Lia Williams enter in matching black trouser suits and watch – as do the rest of us via video screens around the theatre – as a “courtier” spins the coin in a bowl. On press night, Williams called correctly heads, which meant she got to play the queen with the power, Elizabeth I; Stevenson removed her jacket and pulled her shirt out of her trousers to show the modestly sorrier state of Mary, Queen of Scots, imprisoned in Fotheringhay Castle.

Icke’s idea in both the casting and the presentation of this moment is that, in Schiller’s 1800 play which imagines a meeting between the two, Elizabeth and Mary are not opposites but complements: two sides of the same coin, geddit? Each is born to command, has a cadre of zealous followers, and each is imprisoned: Mary in Fotheringhay, Elizabeth by the obligations of kingship (at various points, both queens describe themselves in Icke’s blank-verse adaptation as “king”). Icke makes this metaphor visible by ending the play with Elizabeth, her face now white-leaded, being confined in the period gown, farthingale and ruff familiar to us all: she is forced to become “Elizabeth I”. And throughout the second half, each queen in turn walks around the circular stage rostrum whilst her interlocutor revolves in the opposite direction: all these moral and political complexities, wheels within wheels.

I’ve only seen the play (which has transferred from Islington’s Almeida Theatre where it ran to great acclaim over new year 2016/17) one way round, so I can’t say for certain, but my hunch is that the arrangement I saw is the more natural casting. Stevenson has a reputation for being an emotionally free and open actor, so that we immediately feel the precariousness of Mary’s position; Williams, in contrast, is talented at playing characters who show agonising restraint. In each case, though, they get to display the other side as well, as the pressures grow almost too much for Elizabeth and Mary begins to realise the more intangible power she holds.

The supporting cast is almost as strong. They include Rudi Dharmalingam as Mortimer, the jailer secretly on Mary’s side; Elliot Levey as calculating, faithful chief minister Burleigh; Michael Byrne the ageing, desperate voice of reason Talbot; and Carmen Munroe as Kennedy, Mary’s lifelong-unyielding nurse. It’s a fine revival that hides intricacy and thoughtfulness beneath a simple modern-dress surface.

Written for The Lady.