I went to watch The Last Days of Judas Iscariot purely because of the poster. If you haven’t seen it, no prose is going to convey its brilliance. The cast, in various suits, are gathered around a table in an otherwise empty McDonalds. In the middle of the table sits the Jesus from Leonardo’s The Last Supper, his right hand buried in the remains of a reconstituted chicken burger meal.

The blurb to this play promises a ‘gripping yet hilarious drama.’ Yeah, right, an entertaining disquisition on a religious subject with a serious point. The last time I came across an idea like that was in the publicity for Dogma, a film so bad that it actually drags down Adam Sandler’s average. But – amazingly – The Last Days of Judas Iscariot has it both ways. It’s funny. And it’s (fairly) dramatically effective. That it manages to be both is a tribute to a cast full of energy and imagination.

Let’s start with the humour. The script is not promising. For an actor, it takes a great deal of skill to deliver lines like ‘when I come into court dressed as Liza Minelli in a one-piece bathing suit, that’s the day I want your opinion’ and get a laugh out of an adult audience. For a director, it takes even more elan to sculpt Santa Monica as a hoop-earringed Irish harridan in a white-and-gold Adidas tracksuit glowing with Daz whiteness without watching your production crash and burn around you.

But it works. The characters are mostly well thought-out and slickly executed caricatures – the blustery judge, the birdlike Sigmund Freud, and Rachel Dedman’s magnificent power-dressing Satan in four-inch heels – and, most importantly, they are not trying to be heroic comedians. The humour comes from the whole cast. Of course, there are some moments that induce eyebrow-crunching winces. Simon the Zealot swaggers into the court to the thunderous bathos of Gangsta’s Paradise played on the chapel organ. One of the lawyers asks Caiaphas the Elder if there is a Caiaphas the Younger. On the whole, however, the deadpan delivery and relentless pace get belly laughs.

And now for the seriousness. The play opens with real gravity: a single candle flickers, and Iscariot’s mother enters with bruised eyes in a vision of pure torment. ‘I placed my son in a hole,’ she says, ‘and covered him with dirty and rock alone…I grudge God none of this’ – her left hand fumbles with the hem of her top – ‘and though my heart keeps beating only to keep breaking, I do not question why.’

It closes, too, with the pearly-eyed stare of Adam Trepczynski’s Judas, comatose with suffering. In between, the plot is straightforward: Judas Iscariot is on trial. The counsel for the prosecution, Max Gill’s Perrigrew, is a gloriously camp sycophant in a mauve shirt and a loud red tie. On the other side of the courtroom, Evie Jackson is a little mawkish and hesitant as Iscariot’s defence lawyer. But in spite of the mild monotony of the staging and delivery, the play’s serious points come across clearly, and the debate has real moral substance beneath the comedy.

You find yourself drawn from side to side of the argument like a slightly carsick six-year-old in the back seat. Every character presents a compelling ethical defence of his own actions, from Caiaphas’ superb dignity to the brisk pragmatism of the Jock Stirrup-like Pontius Pilate. The play’s ultimate judgement is not an easy one; and at the end you realise that this is because when we judge Judas we judge ourselves. The last, lingering image of Judas’ remorse – ‘take all the sorries in the world and pile them all up on top of one another, and what’ve you got? Nothing, that’s what you’ve got’ – is you, you facing up to your own failures.

In the last speech of the play, the head of the jury describes the happiest moment of his life as ‘peaches and dynamite’ – and peaches and dynamite sums up this production nicely. The Last Days of Judas Iscariot is not prize-winning drama, but it is sweet and sour and powerful by turns, and for a play in a college chapel it is really very good indeed.