As the audience file into the theatre, a man  in a smart grey suit and shiny black shoes (Jamie Griffiths) sits on the stage next to the first slide of a PowerPoint presentation on financial risk. When the door closes and the house lights go down, he begins to applaud us, slow-clapping. The Quant, in many ways, is not a typical theatrical production.

Presented as a lecture from a quantitative analyst at “the world’s second biggest bank”, the audience are cast as new, green trainees. At one point, Griffiths singles out a man in the front row and asks him, “Is your phone turned on?” The man says no. “Why not?” Griffiths demands. “You should be switched on all the time.” The world of banking and the world of theatre might seem poles apart. But at the heart of this production is a dramatic tragedy entirely coherent with classical rules: the story of one man’s aggressive rise to power and his rapid fall from grace. A little logo in the corner of the PowerPoint tells us that we now work for “GoetheBank” – and this is a play about a Faustian over-reacher, a man who is given everything and loses it all.

About 20 minutes into the performance, the lights dim and our sardonic, bullying lecturer becomes a gauche young man with a Welsh accent. In this persona, Griffiths explains the events that led to his current position, and convincingly conveys the excitement and adrenaline rush, the thrill, of high-stakes banking. There’s a strong narrative created in these scenes of the one-man play, revealing a bright, ambitious boy with a first-class physics degree, drawn towards power like a moth to a flame. It’s well-written and well-researched, with enough small details to give the sense of a real life while maintaining a strong pace. I would have liked there to be a bit of more a bleed between the two parts, more of the young man appearing in the older, as the play approached its denouement. It would have lent greater drama to the scenes in which we were given caustic descriptions of other real-life traders – Kweku Adoboli, Jerome Kerviel – whose risks had failed to pay off.

The improvisatory aspects of these scenes were slightly weak and I felt that Griffiths could have done with some more of the confidence of his character at these points. Conversely there were also a few moments of over-acting – a horrified stare of dawning realisation as his financial models begin to go wrong and a stagey grimace at a nasty cup of coffee. These are noticeable because there is only one character onstage throughout, speaking directly to the audience. The production generally, although minimal, is competent and professional, making good use of limited lighting, and Griffiths never lets the stage feel empty, prowling around it in an infinity symbol as he reels off the many factors involved in a major bet.

It’s an enjoyably tense performance, full of nervous energy, the dark portrait of a man embroiled in a system that takes no prisoners. It tells a story that is both highly topical and as old as time.

The Quant is playing at the Old Red Lion Theatre until 20 July. For more information and tickets, see the Old Red Lion Theatre website.