By Nick Curtis

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Four Irish blokes exchange well-worn banter and ghost stories in front of a bemused young woman while getting steadily inebriated in a grotty rural pub outside Carrick. It’s not the most thrilling premise for an evening in the theatre. Yet Conor McPherson’s much-revived 1997 play is rightly considered a modern classic, and beneath the gentle comedy is a study of small acts of connection between characters who are lonely or grieving.

It’s aged better than other explosive early works by young writers that emerged from the powerhouse of the Royal Court in the mid-90s. If this current revival directed by McPherson seemed a little undercooked on opening night, The Weir retains its power to beguile and unnerve. It also proves a splendid vehicle for the mighty presence of Brendan Gleeson, making his West End debut at the age of 70.

The veteran character actor plays Jack, owner of a remote garage, first seen alone, trying and failing to pour a pint of Guinness for himself from a recalcitrant pump. It’s that kind of pub. There’s a peat stove in the corner, ancient photos on the walls, the few regulars get stuck into the stout and the Paddy whisky (“small one?”) and conversation runs on well-worn grooves. Everyone knows everybody else’s business. The wind is supposedly howling outside, and though the outside geography is vividly evoked, the pub feels hermetically sealed from the world.

When laconic barman Brendan (Owen McDonnell) arrives, Jack warns him that local boy-made-good Finbar, now a Carrick hotelier with a property empire, has rented a long-empty nearby house to an attractive Dublin woman. Apparently enamoured, he’s bringing her to the pub. This prompts mild disapproval from Brendan, more for the disruption it will cause to the normal arc of an evening than for the fact that Finbar is married. With Jim (Seán McGinley, a stolid, ageing odd-job man with an ancient, ailing mother, they agree that Finbar is a terrible bollix.

And so he proves, in the person of Tom Vaughan-Lawlor, clownishly hyperactive in his naff beige suit, humming Fairground Attraction’s 1988 hit Perfect to himself and occasionally loosing off a series of kung fu kicks. This is for the benefit of Valerie (Kate Phillips), whose apparent easygoing serenity is deceptive. Some old, spooky stories are trotted out, laying the ground for the revelation of something truly awful.

McPherson’s particular talent as a writer is his ability to build and then subtly alter atmosphere. Countless small details accrue to build up the mood of the pub: the parsimonious doling out of a pack of ten Silk Cut; Brendan repeatedly “debating” whether to join his customers in a drink; the resentment of foreign campers universally dismissed as “the Germans”; the derision levelled at anyone – like Finbar – who drinks Harp lager rather than the black stuff.

The humour is slow-building too, woven into the verbal tics and cadences of characters that McPherson knows inside out. He wrote The Weir after transferring a series of successful monologues from Dublin to London to prove to critics – and how – that he could write dialogue. But he loves storytelling too, and here the ghostly tales emerge from the pub blather to hold the listeners, on stage and in the audience, rapt. They’re ostensibly innocuous – a tapping at a window, the apprehension of a presence on the stairs – but they exert a frightening power.

The cast, all fine actors, did not seem totally on top of their words on press night, but you could put that down to the effect of the Paddy on the characters. All, however, are magnificently still and focused when listening. Gleeson, with a face like a scowling thunderhead and a swept-back russet-grey mane, bears an unnerving resemblance to Donald Trump, but once you get over that he’s a delight to watch and hear. Jack’s late monologue about the woman he once loved, is spellbinding.

The quality of McPherson’s writing is distilled in a single line: “There’s not one morning I don’t wake up with her name in the room.” Lovely.

The Weir at the Harold Pinter Theatre, until 6 December, theweirplay.com.