Unbelievably, until late last year I’d never read Harper Lee’s classic novel, To Kill a Mockingbird. (My school made us study Of Mice and Men instead.) And so, in a moment of madness, I decided not to see the production at the Regent’s Park Open Air Theatre in 2013 – then regretted it, when everyone started telling me how good it was.

Well, I wasn’t going to make that mistake again, so when the production transferred to the Barbican at the end of a national tour, I jumped at the chance to go and see what all the fuss was about. And now I get it.

For anyone else like me who’s been in the dark all this time, To Kill a Mockingbird is a story about innocence and injustice in the Deep South, seen through the eyes of a young girl, Jean Louise ‘Scout’ Finch. Scout and her brother, Jem, live a comfortable life in the small town of Maycomb, surrounded by the eccentric townsfolk and morbidly fascinated with their reclusive neighbour, Boo Radley. Then their father, Atticus Finch – who both children think is pretty old and boring – is hired to defend Tom Robinson, a black man accused of raping a white woman. Suddenly Jem, Scout and their friend Dill are exposed to a new world, in which an innocent man can be condemned because of the colour of his skin, and the most unlikely characters can suddenly become heroes.

The charm of the novel lies in its narrator, Scout, who makes us reconsider the horrifying events of the story from a child’s perspective. Timothy Sheader’s production captures that childlike spirit to perfection, as the company take it in turns to read aloud from the novel, slipping into costume to play their part in the story, and crawling around the stage on their hands and knees to draw a rough outline of Maycomb in chalk.

The three young stars of the show – on this occasion played by real-life siblings Jemima and Harry Bennett, with Leo Heller as Dill – give incredible performances. I couldn’t believe it was Jemima’s professional debut; she’s warm, funny and has all the simple innocence of a child, and yet there are moments, particularly when dealing with the men in her life – Jem, Dill and Atticus – where a matter-of-fact young lady can be glimpsed hiding just beneath the surface.

Meanwhile, the true hero of the story, Atticus, is brought to life by Robert Sean Leonard. Seen first through the eyes of his children, he seems a little dry – but his wry smile, and, later, his fierce passion as he stands up for what’s right, soon reveal him to be a far more complex character. Leonard’s performance is spellbinding; I’ve rarely heard a theatre so silent as the moment when he sums up his defence case, with the desperate look of a man who knows it’s probably futile, but is determined to try.

What I enjoyed most about this production, though, is its loving homage to the original text. Each member of the company, as they file on to the stage, picks up a copy of the novel and holds it aloft in a silent salute, before beginning to read. There’s no need for a fancy set or dramatic effects – the production allows Harper Lee’s work to speak for itself in a faithful retelling of a classic story. After all, why change something that was already perfect to begin with?

If you get the chance to see this production before it closes on July 25th, don’t pass it up, because you might live to regret it. To Kill a Mockingbird, like the novel on which it’s based, is deeply troubling and yet, at the same time, utterly charming. It makes you question things that as adults, we tend to take for granted, and leaves you feeling a little like a child yourself. But I think we all need to feel that way from time to time; being a grown up is overrated.