Following the death of her son, Mary finally gets her chance to speak in Deborah Warner’s powerful staging of Colm Toibin’s book. The incomparable Fiona Shaw gives voice to Mary as a weary, grief-stricken, angry women. A mother, certainly, but not the mother of God.

From her incredulity that a man presumes to tell her the cicumstances of her son’s conception, to her guilt at having run away rather than staying to watch him die, Shaw is a revelation. For an hour and twenty minutes she speaks, rocks, gestures, and holds the audience in the palm of her hand. From the moment she starts to speak, you almost forget to breathe.

We all, religious or not, know the story of Jesus’s crucifixion. We know about the mockery and the crown of thorns, the spear to the side and the nails hammered through wrists and feet. But to hear that story told through the mother’s eyes, to feel the man’s pain through the words of the woman who gave birth to him, gives a whole new dimension to the familiar events.

What stops this from becoming mawkish or evangelical, though, is a mixture of Toibin’s writing and Shaw’s stunning stage presence. This Mary is ambivalent at best about her son’s miracles, remaining unconvinced of his abilities to heal the sick and raise the dead, and skeptical about his followers and their motives. She is understandably bitter, too, which makes her feel very real and relateable – nothing is sugar-coated or glossed over, meaning that your respect for this woman grows as the evening goes on. Her descriptions of the resurrected Lazarus, dazed and confused, are particularly affecting.

Underscored by Mel Mercier ‘s unsettling, shifting soundscape, Shaw tells us, and the world, her version of events. Tom Pye’s set is scattered with chairs, water jars, a ladder, all of which are both part of the scenery and part of the story. We know what’s going to happen, of course, and the skill in this production is in still gradually building the tension, in keeping us guessing even when the inevitable happens. Mary’s take on events is consistently off-beat, surprising, even humorous at times. The production also captures the pettiness of family gossip against the story that changed the world.

Shaw presents us with a confused and grieving Mary, trying to stay strong and centred as the world she has known crumbles around her and she tried to process her anger. By confronting the discrepancies in the story and the human side of the crucifixion – a mother watching her son die, slowly and in pain – The Testament of Mary becomes and powerful and unexpected show.

The Testament of Mary is at the Barbican until 25 May. For more information and tickets, visit the Barbican’s website