The central question of this play hangs on a mathematical proof, a paper found in her father's office following his death, which details a potentially ground-breaking new mathematical theory. The problem of proving the paper's ownership then follows.

Sian Goff & Julian Richards
Sian Goff & Julian Richards

It's a dry concept, but David Auburn's play is sublimely written, both heartbreaking and challenging. It was adapted into a hugely successful film starring Gwyneth Paltrow, so is an ambitious choice for Reading Rep, the emerging South-East company now in its second season at Reading College's studio theatre.

Overall, artistic director Paul Stacey's production is a huge success; urgent, engaging and touching. The cast are excellent, although appearing nervous to begin with, and their characterisations are utterly believable.

Some of the staging feels slightly unnatural, particularly when the cast sit on the front of the stage, but generally this doesn't detract from the action and is presumably down to space restrictions.

The set design, by Victoria Spearing, is convincing, but the lighting design (Russell Pearn) is the production's biggest hindrance. The cast work hard to sustain and build pace, rhythm and energy throughout the scenes, but long and slow transitions (both in the lighting and in direction) somewhat cause the tension to dissipate between them. That's my main criticism though, of what is overall a very strong production.

Siân Goff is a good Catherine, choosing to place the moody-teenage elements of the character centrally, an interesting interpretation, and one she delivers believably throughout. However the deeper elements of her person, such as her struggle with identity and mental illness are somewhat under-explored.

With a little more maturity and experience, I don't doubt that Goff will become an accomplished performer. For me though, her Catherine occasionally comes across as one-dimensional, and her motivations and thought processes seem a little vague at times. That said, her stage presence and focus is excellent.

Highlights come in the flashback scenes, particularly in the development of the romance between Catherine and Hal (an earnest yet gentle performance from Kyle Fraser), which in "real-time" isn't quite as natural.

There's a brilliantly-pitched performance from Julian Bird as Robert, a hugely intelligent man who is unable to make his mind ("machinery") work in the way it once did as he slips into the depths of mental illness.

The stand-out performance though is from the astonishing Kate Tydman as Catherine's sister, Claire. The relationship between her and Catherine is perfect, and Tydman's tone and expressive vocal range are flawless. Tydman's energy and commitment fill the theatre, and she is utterly engaging throughout.

The whole cast light up when they're working as an ensemble, and that tone of love and respect between all the characters is testimony to Stacey's hard work and skill on the development for this project.

I highly recommend this production, it cements Reading Rep as a talented and versatile company, who I don't doubt have very exciting things to come.

Proof runs at Reading College's Studio Theatre until 19 April