The most striking aspect of Peter Cook’s powerful one man show Breaking the Castle is its authenticity. When the protagonist David tells you what it’s like to take drugs, you don’t need to have read the programme to understand that this is a man who knows what he’s talking about. The show charts David’s journey through and beyond addiction, and was inspired by true events in writer and performer Peter Cook’s life, which gives the writing an undeniable authority and makes it a gripping watch from the start.

David is a struggling actor who spends half his life at home waiting for calls from his agent, hoping that today might finally be the day he gets to play Hamlet instead of a dying cockroach. To pass the time until that day arrives, he takes drugs, and drinks, and gambles, and has sex – and then takes more drugs… Until one day he finds himself sitting in a rehab centre in Thailand, where a passionate counsellor shows him it’s possible to break out of the vicious cycle of his addiction, and make a new place for himself in both the world and his own life.

The action is fragmented and the pace frenetic as we skip backwards and forwards in time, with scenes depicting David’s rehab journey starkly contrasting against some of his lowest moments back home in Australia. Peter Cook is an engaging and energetic performer, throwing himself – sometimes literally – around the litter-strewn set and playing a multitude of characters with a multitude of accents. (In fact the number of different accents begins to be a bit distracting, and Cook’s at his strongest when playing characters who have distinctive physical characteristics – a fellow addict on the streets of Sydney’s Kings Cross and a patient he encounters during a hospital stay are particularly well depicted.)

The second half of the show brings a number of revelations about repressed childhood trauma, allowing both David and the audience to make some sense of how he got to where he is – and a recurring theme featuring butterflies injects an element of hope. There’s a surprising amount of humour, too; David’s description of his addiction is frank, honest, without a trace of self-pity, and when he smiles his whole face lights up. All this combines to make a character we can really get behind, and his evident joy in the play’s final scene is infectious.

It also helps to bring home a key message in Cook’s writing: that people who struggle with addiction are just that – people, and just as the power to acknowledge and move past it lies primarily with the individual, so the rest of us have a responsibility to look beyond our own judgment and try to see the person instead of the disease. Powerful, funny and deeply personal, Breaking the Castle has a lot to say – and it says it very well.

Breaking the Castle continues at the Old Red Lion Theatre until 11th November.