There’s a particularly poignant moment in Niall Ransome’s FCUK’D, in which two frightened boys huddle together under a railway bridge in the freezing cold, while above them commuters are absorbed in their phones and Christmas revellers make their merry way home, all of them oblivious to the children who need their help just yards away.

While this image has plenty to say about our society and way of life, it’s also a pretty good metaphor for the show itself. While other theatres opt for the crowd-pleasing spectacle of panto, not far away The Bunker is quietly doing something very different to mark the festive season – reminding us along the way that not everyone is celebrating just because it’s Christmas. FCUK’D is a simple, understated yet incredibly hard-hitting one-man show about seventeen-year-old Boy and his little brother Matty. Having been abandoned by their father and neglected by their mother, Boy lives every day in terror of Matty – the person he cares about more than anyone else in the world – being taken away. And he’s willing to do anything, even go on the run, to prevent that from happening.

However touching Boy’s motivation, when it inevitably happens the two brothers’ flight always seems like a doomed enterprise. Boy is, by his own admission, rash and immature; he has no idea what he’s doing and is clearly as terrified as his confused little brother. Driven by desperation and fear, the pair have no money, shelter or transport and are forced to take increasingly extreme measures to survive in the freezing December temperatures. Their devotion to each other is such that we want them to make it, and yet we have to acknowledge their situation is unsustainable, and to question if this really is the way to give Matty his best chance – even if the alternative is a system that isn’t doing enough to help young people in trouble until it’s too late.

Will Mytum gives an utterly compelling solo performance as both Boy and Matty (he even has a convincing play-fight with himself at one point). Delivering Niall Ransome’s rhyming verse in a way that highlights the poetry but still sounds completely natural, Mytum has all the swagger and false confidence of any teenager, but with a haunted expression that reveals the self-loathing and insecurity lurking not far beneath the surface. Then, all of a sudden, it’s like a switch is thrown as he transforms into Matty and we see all the fear and doubt fall away. Matty is adorable – innocent, inquisitive, and with such absolute faith in his big brother that he’ll follow him anywhere, no matter what it might cost.

The rest of the production, which is also directed by Niall Ransome, is similarly understated, with effects that – unlike in many festive shows – support the central performance without trying to be the main focus. Peter Wilson’s ominous score helps to build the tension, while the set by Grace Venning captures the harsh urban environment of Boy and Matty’s world. And Jess Bernberg’s brilliantly effective lighting combines with Ransome’s words to show us things we can’t see, like the flickering orange of a flame, or the blue lights of an approaching police car.

FCUK’D is not your typical Christmas show, but that’s not a bad thing; pantos are always good festive fun, but they’re also about as far from the real world as it’s possible to get. At this time of year perhaps more than any other, when we can get so absorbed by shopping, wrapping, cooking and partying, a shot of reality – however sobering – might be just what’s needed.