From supping fine wine and cooking gourmet fish dishes to appreciating the finer points of Chopin nocturnes - one thing you can’t accuse Father David Anderton of in Ian McDiarmid’s stage version of Andrew O'Hagan's Booker Prize-nominated novel is leading a life of Roman Catholic piety.

Assigned to a declining parish in an Ayrshire coastal town where working class bigotry, tartan tribalism and economic depression are embedded in the communal gene pool, Father David may be spiritually directionless, but at least he arrives complete with his own antique chandelier, a posh English accent and a natural ability to wind people up, all of which sets him completely out of sync with the the hard-boiled Scots he’s supposed to serve. Combine this unholy lifestyle with a sex scandal involving drugs, booze and a tender drunken kiss with a cocky special needs schoolboy he’s grown rather too fond of, and the 60 year-old finds himself hurtling headlong into a small-town Purgatory reserved for “peedo” priests.

McDiarmid stars in this National Theatre of Scotland co-production as the closeted cleric with one foot trapped in the past – a fascinating mess of contradictions who never moved on after losing his moral compass somewhere back in the idealistic Sixties when Conor, the only real love of his life, died in a sudden car crash. But while McDiarmid puts in a stunningly subtle performance, conveying the celibate priest as a naïve, prim and emotionally reserved victim of his own secrecy, his stage adaptation of O’Hagan’s prose takes most of the first act to begin to get near to the beating heart of a lonely man completely adrift in a godless community.

Once the fatal fumbled kiss has been planted, any gap between novelistic psychological study and social document very quickly merges and John Tiffany’s production on an open Donmar stage creates an extraordinary sense of theatrical tension and a genuine feeling for flawed humanity, complete with a chorus of gossiping parishioners whose hymn-singing seamlessly segues into militant IRA anthems and obscene football songs, and a brilliantly acted dinner party scene where the priest’s liberal Sixties politics seem like yesterday’s stale leftovers.

With superbly drawn performances from Blythe Duff as the cancer-ridden housekeeper who eventually pierces Father David’s emotional armour, Colette O'Neil as the novelist mother who provides his only reality check and Richard Madden as his chaotic schoolboy nemesis, the end result is an absorbing morality play that eventually gets almost too close for comfort in these morally ambiguous times – whether you’re a Scot or a Sassenach.

- Roger Foss