It’s unusual, even in this day & age, for a play’s two lead roles to be played by women – and it was even more unusual 200 years ago, when Friedrich Schiller wrote his classic play ‘Mary Stuart’. Not that he had much choice about the sex of its protagonists: its plot concerns the two most famous women of their time: Elizabeth I and her cousin Mary Stuart, the ousted queen of Scotland with a valid claim of her own to the English throne.

The two women never actually met, despite Mary’s incarceration in England for 18 years, but historians and lovers of the Tudor period have long imagined what might have happened should such an encounter have taken place. It is this much-imagined meeting which forms the basis of the play, brought up to date by the Almeida Theatre with a very modern twist: the toss of a coin, at the beginning of each performance, determines whether Juliet Stevenson or Lia Williams play Elizabeth or Mary.

The night we were there, Juliet Stevenson was awarded the role of Mary and Lia Williams that of Elizabeth. I’ll be honest, I was hoping it would be the other way around, although I can’t quite articulate why: I think it must be because looks-wise Lia Williams resembles Mary more, tall and dark-haired as she is. Perhaps that shouldn’t matter, but it was at the back of my mind as the lights went down.

Most of my preconceptions vanished the moment the play began, however. It was ELECTRIFYING. What a gripping three hours of theatre, and impeccably acted: both actresses were superb, as was every member of the impeccable supporting cast. This is a story that will never grow old – how can it, when its themes remain so relevant? Politics, jealousy, power, religion, the division between Scotland and England…its events could be taking place right now.

Schiller’s writing, mirrored by Stevenson’s portrayal, treats Mary with compassion, demonstrating how, to a great extent, she was manipulated by the scheming (male) politicians around her and highlighting how the circumstances of her captivity led to her downfall: boredom, frustration and a genuine belief in her own right to rule all played a part (as did her terrible taste in men – but that element is glossed over). It’s impossible not to feel some sympathy for this flighty, headstrong, but highly intelligent woman who was separated from her son when he was just two years old, never to see him again.

Interestingly, the play is less kind to Elizabeth – as played by Lia Williams she is waspish, indecisive and judgemental. Yet she, too, is a prisoner, albeit of a different kind – the constant fear of assassination attempts mean that her movements are almost as restricted as Mary’s. This is where the brilliant, claustrophobic set comes into its own – we are left in no doubt as to the impact the confined setting has upon both women. Laura Marling’s specially composed music also plays a key role – this is the first play I’ve been to where music is played through the duration, and it works a treat. A brave move by the Almeida – and one that definitely pays off; the haunting score stayed with me for hours afterwards.

Ultimately, of course, only one woman can win this particular power struggle. Heads must roll – and it is Elizabeth, the consummate politician, who will triumph. This play, too, is a triumph – its acting, staging and production were all of the highest order and will remain in my mind for a very long time to come.