Faith Healer is a classic Oirish wrist-slasher about three sponging half-wits caught in a downward spiral of penury, booze, squalor, sexual repression, bad healthcare, murderous violence and non-stop drizzle. The mood of grinding despair never lets up for a second as the healer, Frank Hardy, along with his moaning wife and their Cockney sidekick, motors around the British Isles trying to cadge pennies from cripples in exchange for bogus cures. Every cliché in the rich thesaurus of Celtic misery is brought together in this rancid melodrama about mob justice.

Every cliché in the rich thesaurus of Celtic misery is brought together in this rancid melodrama

Brian Friel’s play premiered in 1979 on Broadway, but the action is set in the early 1950s and the culture it describes belongs to medieval times or even the Dark Ages. From a lofty height, Hardy pours scorn on superstitious and ignorant Celtic bumpkins, all oppressed by incurable diseases, and all eager to find salvation in the blessings of a fake miracle-worker. The play doesn’t limit itself to Ireland but visits the beautiful valleys of west Wales and north-east Scotland as well. Some of the Welsh locations are prosperous seaside towns bustling with shops and restaurants, but Friel’s script doesn’t want to let a cheery fact get in the way of a depressing speech. Wherever Frank wanders, he finds oafish savages sinking in stupidity and self-neglect. Poor guy. He must have been a nightmare to go on holiday with.

The production, directed by Rachel O’Riordan, is masterfully realised. The stage, adorned with a few wooden chairs and Frank’s tatty banner, is an austere confection of burned gold, black and grey. Lovely to look at. Declan Conlon (Frank) bewitches us with his blarney and his apparent candour as he describes the broken and resentful invalids he tries to cure. He exits the stage and his wife, Grace, arrives to deliver an account of their story that differs radically from Frank’s. This may explain the show’s appeal – it energises us and turns us into sleuths who have to tease out the reality from the concealments and half-truths offered up by the couple.

Justine Mitchell gives the best performance as Grace, the play’s most tragic figure, an articulate and expensively educated beauty who risks everything when she hitches her star to the sozzled, ruined Frank. Finally comes Teddy, a Cockney impresario, whose patter adds a fresh layer of clues and obfuscations to the yarn. His cheeky-chappy speech includes daft jokes about a menagerie of performing animals including a dog that plays the bagpipes – and even practises in its spare time.

It’s the fault of the script that Teddy’s stand-up routine doesn’t match the fatalistic gothic mood that pervades the rest of the piece. The story peters out with no proper ending and a lot of unanswered questions. What actually happened to Frank? Who fathered the baby? Where are these characters located? Are they speaking to us from beyond the grave? Why? This wretched and frustrating play, along with Friel’s Dancing at Lughnasa, is wildly popular with those who regard the Irish as a gang of penniless, parasitical, self-victimising deadbeats. Its influence is probably strongest where contact with real Irish people is weakest. The best advice is to treat it like a minor operation that you’ve postponed once too often. Book the appointment. Get it done. You’ll hate every second of it but trust me, you’ll feel better afterwards.

Police Cops: The Musical is an astonishing piece of light-hearted satire. The show, set in the 1980s, gently mocks every cliché in the lexicon of investigative fiction. The hero is a humble waiter who joins the force after making a vow to his dying father. He teams up with a grizzled, ill-tempered, hard-drinking veteran who was kicked out of the police department many years ago for unknown reasons, although he insists that he quit voluntarily.

Together they set off to apprehend the elusive leader of a Mexican cartel who bears an uncanny resemblance to the chief of police. The show announces its sense of mischief in the opening scene when a criminal is gunned down in the gutter, but the arresting officer pumps several more bullets into his corpse, just for fun, because that’s how real cops behave.

The five-strong company is led by Zachary Hunt, who looks like the frontman of a boy band and is blessed with fabulous dancing and acrobatic skills. The show is a treasure trove of visual effects and inventive theatrical gags but it offers more than just a feast of comic delights.

It feels like a campaigning show that dares to carry us back to a simpler world where law enforcement meant the triumph of right over wrong. Good cops used to bust wicked felons. End of story. Nowadays, the cops are a gang of fascist pigs who terrorise hapless criminals suffering from undiagnosed emotional disorders. If you hate the culture of modern policing you’ll love this show.