At the heart of I Saw Myself is a woman - a powerful, self-aware, sexual, physical woman. This is Eve before she was castrated by the Abrahamic religions. She's not good, but she is strong, and glories in that strength. She's a Western Kali - whether she uses her power for good or evil is, to her, incidental.

The woman, the queen, is Sleev, played here with passion and breath-stopping charisma by Geraldine Alexander. As the playwright Howard Barker writes in the introduction, "we know the epic status of the faithful wife." Here he grants the same to the faithless. As Sleev not so much says but proclaims: "I'm not Penelope, that flaccid packet of fidelity."

Sleev manipulates the women and men around her like sacrificial pawns. She's super-intelligent, manipulative, and magnificent, and with a different set of genitals she'd have made a superb king - a young Hal, but with brains. She plays games to stave off ennui, and is disappointed that no one can compete. We get little sense of her husband, killed in battle, but he was obviously no match for her. The only person in this troubled court who sees through her - though is still unable to resist her because of the barrier of class - is her "best maid", Ladder, played with sophisticated, passionate restraint by Jules Melvin.

This is a grand tragedy, in a tradition familiar for more than two millennia. Yet there's something new and fresh in the previously unstageable honesty and the preparedness to see and engage with women on their own terms. (It's hard to believe it was written by a man.) Unlike their predecessors over many centuries, these characters aren't trapped by stage convention into being metaphors and symbols for sex; when they talk about sex, when they have sex, it's presented in all of its full frontal humanness.

There's also great sophistication in the chosen setting, an unnamed medieval court, which allows the great feminine metaphors of weaving and sewing to fit within a naturalistic frame. It allows too the introduction of the sophisticated symbolism of the period — you'll think often of the Lady and the Unicorn, and the Bayeux Tapestry — with drooping or perky black roses, frisky otters, and rampant weeds.

I'm not an expert on medieval tapestry, but if this play's description of its conventions isn't entirely accurate, it certainly feels true. We hear how the main narrative of the tapestry is by convention a story of men's lives, of battles and kings, with women's lives fitted around the edges. It's hard not to cheer when Sleev proclaims, "The subject of the great stream will be me." "Never has the life of a woman filled the great stream."