Referendum fever reaches Stratford East. Spoiling, by John McCann, takes us into the corridors of power in Holyrood shortly after a triumphant Yes vote. We meet a foul-mouthed bruiser named Fiona whose strident views and vivid language have propelled her into the public eye during the referendum battle. Her reward is Scotland’s foreign ministry. The most obvious and striking thing about Fiona is her personal ghastliness. A coarse, petulant show-off, over-endowed with self-belief, she has no wit, geniality or political intelligence. Asked how she feels about the birth of Scotland’s liberty, she rasps out her reply like a seagull with tonsilitis. ‘Rebirth!’ Her mistrust of Westminster is deeply engrained. ‘They’re punishing us in the settlement talks,’ she gibbers, ‘because they can.’

Her sense of victimisation is stoked by the play’s absurd storyline. Fiona is due to host a joint press conference with her counterpart, the English foreign secretary, when she discovers that meddling Londoners have doctored her speech and included the word ‘interdependence’. Diplomacy, of course, would never countenance such an abuse. A sovereign nation may say what it pleases without interference from a foreign power. But this plot twist gives Fiona a chance to reveal her view of independence: it’s all a big con engineered by rapacious English schemers who intend to carry on bullying and plundering Scotland in perpetuity. ‘We’re not independent,’ she squawks. ‘We’re indentured.’

Are the Scots really as small-minded and mistrustful as this? The writer, an Ulsterman, may have misread the situation and delivered an appalling libel on Scotland’s political culture. But only last month the play won a Fringe First award from the Scotsman, which suggests there are some up there who applaud this sort of chippy, hate-fuelled sectarianism. And neutrals, like me, are bound to conclude that the Yes campaign harbours a perverse desire to remain in the Union. Membership of the United Kingdom gives pessimistic Scots an excuse to contemplate a malign deity (known as ‘Westminster’), which explains every setback in their daily lives, and acquits them of responsibility for their personal failings. Liberty should be about optimism, innovation and open-heartedness, and the best of the Yes campaign endorses those ideals. This manipulative rant argues that a free Scotland will wallow and flap about in a toxic birdbath of misery and paranoia. That’s rubbish, I hope.

Finborough Theatre specialises in acts of reclamation and its latest salvage job brings Robert McLellan (1907–85) to the attention of west London. The Flouers o’Edinburgh is set in the mid-18th century when Scots identity was under siege from its richer and more powerful southern neighbour. Charlie Gilchrist, a young Scottish toff, returns from England eager to show off his sophisticated London accent. Cue shock and outrage from his friends and family. But Charlie’s on to something. He plans to buy himself a seat in Parliament where any Scotsman rising to speak in his native tongue is invariably jeered into silence.

McLellan’s drama is written in Scots dialect, which takes some time to acclimatise to. Eccentric vocabulary abounds. ‘Braw’, nice; ‘muckle’, much; ‘windae’, window. But once you’re tuned in, the play is a treat. McLellan’s sympathies are firmly with the Scots who uphold their spoken traditions and he has fun mocking the pretensions of social climbers. There’s a morose but narcissistic poet, Daniel Dowie, whose work ‘The Tomb’ has won admiration in Edinburgh but not London. The monosyllables ‘breast’ and ‘feast’ have the same vowel sound in Scots: ‘ee’. So the English critics mock Dowie’s verses for their hilariously inaccurate rhymes. This sounds abstruse but it works superbly on stage.

McLellan shapes his story around a pair of on-off romances and he uses suspense and surprise reversals with great effect. The play drags a bit in the middle but the final act delivers a series of clever comic twists. Designer Philip Lindley’s compact and stylish set is excellent and I’d recommend the play without reservation if it weren’t for the raucous and lopsided acting. Too many cast members strain to find laughs where there are none. A performer should never select a gesture or a vocalisation that lies outside his natural repertoire of behaviour. Here, half the company leap about the stage grimacing and gesticulating like a set of gibbons dismantling a grand piano. Yet some of them (notably Jenny Lee as Girzie, Kevin McMonagle as Sir Charles, Tom Durant-Pritchard as Simkin and Andrew Loudon as Baldernock) deliver well-observed performances in a relaxed and truthful manner. God knows how the wildlife failed to copy their example. That said, wherever McLellan is next revived, I’ll be first in the queue.