Tom Sergeant – the name suggests authority and the imposition of will, as well as perhaps a certain lack of imagination – is a London businessman who has expanded his business to a chain of restaurants and hotels during the Thatcher years of the 1980s. His swagger ("Fucking gardening! If I could make it illegal, I would!") and ballooning sense of arrogant entitlement ("I'm a doer, I make things happen!") would make him offensive to the point of repulsiveness ("That's how you get women into bed: by listening to their problems") were it not for an aura of power, the sort of thing exercised by Bill Clinton over Monica Lewinsky. He once magnetised Kyra Hollis, a waitress of 18 when he was already 40ish and married. Their six-year affair ended in circumstances which I won't reveal even though this is not a plot-driven drama. Now the two come together in Kyra's little flat to rake over the embers.

Kotei Productions' version of David Hare's 1995 play is a mix of psycho-drama and political comment that's lost none of its force and pertinence, especially right now as the post-election blue corner (privatisation and market efficiencies) bickers with the red corner (nationalisation and Rousseau's social contract) – a two cultures dichotomy.

In the opening scene between Kyra and Tom's son Edward, the bare bones are laid out. He has come to express his pain, to seek understanding, perhaps to apportion blame. Already we're plunged into the landscape of guilt and examination of people's capacity or incapacity to change that tends to form the bedrock of marital psycho-dramas. Interestingly, given David Hare's history of angry social comment, a third almost conventional component, naked anger, is (to my mind refreshingly) absent. Indeed, blackish humour all but takes the place of rage, and director Hugh Tappin told me afterwards he had tried – in my view successfully – to prick what could have been fairly grim subject matter with little darts of levity.

The entree done, thereafter the dynamic of the play is largely a contest between businessman and teacher: poor versus rich, fidelity versus adultery, nurture versus abandonment, although a charming coda courtesy of the Ritz Hotel strikes an entirely different note of pleasure and giving that sent us away into the balmy June night in an unfeasibly cheerful frame of mind.

It's obvious this has been a labour of love by director Hugh Tappin, and his crew, with Natalie Lauren not content to play just the heaviest acting role; her name is all over the programme in several capacities (and she was taking her finals just before the opening night!). Mr Tappin even had the boldness to induce David Hare and actor Bill Nighy (who has twice starred in revivals of the play) to come down from London to advise. Signs of thought and imagination are everywhere. The set is a cramped, upstairs flat, winter heating turned off in the interests of economy. Cleverly put together – deal table, leather armchair that's past its prime, portable turntable and a plausibly-equipped kitchen corner in which Kyra prepares and cooks up a spag bol in front of our eyes; wonderful multi-tasking! Bursts of ambient electronic music, few but telling, punctuate the dialogue; not off-the-peg but specially put together by Jack Trzcinski. The lighting is three burning, naked light bulbs hung unblinkingly over the set, as watchful as Siamese cats observing heedless mice. There's even a neat and helpful little A6 programme – other student companies please note.

As Edward, Luke Wintour bore his hang-ups lightly and plausibly, and his exit in scene 1 was nicely judged, taking his leave calmly and politely, then in a sudden explosion: "Kyra, will you help!" But in the end the show stands and falls on the performance of its two lead actors and here Mr Tappin is very strongly served. Natalie Lauren in her killingly heavy role - she looked exhausted afterwards – is a deceptively serene presence, if anything underplaying the character's guilt over committing the act that caused her to flee Tom's home. Acting with facial expression almost as much as words, she glides round the cramped room as the dialogue ebbs and flows, keeping her end up against this confident, masterful ex-lover. There was a just a short period immediately after the interval where I would have liked just a tiny bit more zip in her output. Otherwise this was a strikingly sympathetic and assured performance. As Tom, Adam Diaper managed the difficult switchbacks of the character with polished ease, getting better and better as the play went forward. Alternately sympathetic, blustering, repellent, almost menacing and then pathetic, Mr Diaper's performance was a lesson in how to translate thought about the character into skilled performance.

Even where there is great love, Mr Hare suggests, not everyone can get along. The first night audience of 44 was rapt for the whole, longish running time, drinking in the tension and emotion. Skylight is serious, adult drama staged here with the sort of intelligence and flair that brings the student drama year to a super-strong conclusion.