Out on Gloucester Green at 7pm, the sun was still shining, and Oxford’s alfresco café culture was in full swing. Young lovers were dunking straws in their Aperol Spritzers. All was right with the world.

Meanwhile, just a few steps away, in the Burton Taylor Studio, By Proxy was painting a much darker picture. Less café culture; more coercive control.

At barely 60 minutes, this is a little gem of a play from first-time writer and director Imee Marriott. It traces the relationship between two teenagers, Kit and Jo, as they leave school, go to university, and start to make their way in the world (or not). As happens with so many school friendships, their paths diverge, and what was once a deep bond of love ultimately evaporates. In the case of By Proxy however the parting of the ways between Kit and Jo is cataclysmic, psychologically disturbing, and complicated by betrayal, obsession and terrible secrets that only surface when it’s too late.

Given that this play deals with such subjects, and even addresses suicide, rape and depression head-on, it’s surprisingly funny. The dialogue is brisk, smart and witty, and there’s even some well-timed physical humour involving Newcastle United shirts. At the heart of the whole thing are the performances from Edie Critchley and Maisie Lambert, both of whom are frankly remarkable. Critchley’s evolution from gossipy schoolfriend to dead-eyed careerist is convincing and uncomfortable to watch. And Lambert is a revelation as Jo. She crumbles as a personality before your very eyes, and the scene where she is on the phone to a distant and detached Kit, desperate for sympathy, knees shaking, trying to reveal something she cannot bear to say, is heart-breaking. There is a sense from Lambert that she is growing as an actor with each production she appears in (I’ve seen her in a couple before this), and it’s a privilege to witness that progression.

This was the first night, and there were some major technical issues which I hope get solved, as they went right to the heart of the play. The main feature of the set is a projection screen which should (I assume) flash up images that illustrate or comment on the action. This only happened once or twice tonight, when we were treated to a brief image of brooding beefcake Pedro Pascal, and a single text message. Both of those moments hinted at what might have made the production even more special. Before the show started the audience watched while, on the screen before us, the determined and blameless tech team sent increasingly desperate text messages to people who might be able to help – but ultimately couldn’t solve the issue. In a way, those unintentionally-seen pleas fitted with the atmosphere and themes of the play itself: cries for help going unheard and unsolved.

Peach Productions has developed a genuine and potent house style. With Wishbone, Every Brilliant Thing and now By Proxy, they successfully focus on traumatic events that ordinary people have to deal with, and they manage to present these stories of pain with panache, poise and power.

There was something in the writing of this show that made me feel it had an autobiographical edge. The programme cryptically says for poppy, and I wondered if Imee Marriott’s fictional Jo might have been inspired by an old friend. If so, I came out feeling that I wanted to say to Imee, you don’t have to carry any guilt. You may have left Poppy behind as a friend, but with this play you’ve shown how much you care, by proxy.