Juliet Stevenson and Lia Williams, Mary Stuart Almeida Theatre. Photo Miles Aldridge

Juliet Stevenson and Lia Williams walk on stage both wearing the same blue velvet trouser suit and a white shirt. Lia calls heads, a coin is spun, it lands and the courtiers bow to Juliet and Lia is stripped of her jacket and shoes and led away. This is the way it will play this time and I am pleased; in my head when I thought of the two actresses I saw Juliet as Queen Elizabeth and Lia as her prisoner Mary, Queen of Scots.

And so the stage is set for Robert Icke's adaptation of Schiller's play of politics, power, religion and family. Elizabeth has kept Mary, her first cousin once removed, imprisoned for many years and is under pressure from her council to do something about her. Mary, through her lineage, has a claim to the English throne, is Catholic seen as a threat to the Protestant Queen Elizabeth.

Mary has been tried in a kangaroo court and found guilty of plotting against Elizabeth but the Queen is reluctant to sign the death warrant. She's also under pressure to marry, itself a political hot potato as without an heir a huge question mark hangs over the succession. Mary, realising she is in grave danger plans, with some trusted sympathisers, to make one final appeal to the Queen.