Karen‘s opening scene drops us straight into the middle of the action; specifically into the middle of a breakup, and a particularly ham-fisted one at that. Our protagonist is being dumped by her four-year boyfriend Joe, and she’s certain that the eponymous Karen is to blame. What follows is a high-energy, laugh-a-minute tussle between inner and outer voices, as the newly-single woman tries to show the world she doesn’t care, while screaming with anger inside. In fact, her thoughts are so consumed by Joe and Karen that we never even learn her own name.

Solo actor Sarah Cameron-West also penned the script, and her writing is a joy. It’s eloquent and creative, fulminating but never bitchy, often branching in unexpected directions or picking hilariously random examples to illustrate a point. Though every word’s perfectly-chosen, she makes them sound spontaneous – and gloriously cathartic too. In a neat recurring gimmick, we often hear just Cameron-West’s side of a conversation, with our imagination left to fill in her interlocutor’s responses; such is the expressiveness of her physical performance, there’s never a moment’s doubt about what’s being said.

Cameron-West engages directly with the audience, recruiting some of the front row to play non-speaking roles – and on the night I attended, the audience enthusiastically engaged in return, audibly gasping at Joe’s cruelty and practically booing at Karen’s. Under Evie Ayres-Townshend’s inspired direction, action drives forward through snappy scene changes, while clever use of lighting signals the contrast between the protagonist’s outer demeanour and her inner thoughts. (Let’s take a moment here to salute the technician, the unacknowledged star of many a Fringe show, who had to be every bit as on-it with the timing as Cameron-West was.)

I did feel the pace and energy sagged in the middle, and the founding premise – that anger can be healthy, and that women in particular shouldn’t be criticised when they embrace it – is a touch underplayed. The ending is fit for the comedy that this is, but it’s too heightened and unrealistic to offer a meaningful comment on life. A more serious undertone, a clearer lesson to take away, would elevate Karen to a five-star show for me.

To be clear, there is some light and shade here: a few moments of unbearable poignancy, one particularly brutal conversation with her loving but judgemental mum. But first and foremost Karen’s played for laughs, and it’s absolutely one of the funniest plays you’ll find this Fringe; the nameless central character is loveable, relatable, and sublimely portrayed. Catch it now – and look out for Sarah Cameron-West in the future.