Between The Royal Hunt of the Sun and Equus, two of the most powerful and serious dramas of the late 20th century, Peter Shaffer dashed off Black Comedy, a slapstick farce that lasted just one act and really had just one funny idea. Shaffer himself was so embarrassed at the simplicity of it that he didn't even want to write the play. But National Theatre maestros Laurence Olivier and Ken Tynan insisted. And thank goodness they did, because that one simple idea is so original, so enticing, and so pregnant with the potential for visual humour, it just demands to be written.

The idea is: it's a power cut. But light and dark are transposed, so when the characters can see, the audience is staring at a dark stage, and when the characters are groping blindly around, we can see everything.

Yes please.

The scenario is no more than a plot to explore and exploit the potential of this wonderful idea. Sculptor Brindsley and his fiancee Carol want to impress her Dad and a visiting wealthy art collector, so they have stolen the neighbour's antique furniture. But hilarity ensues when the lights go out just as everyone arrives.

I should declare an interest here. The last time I saw this play I was in it, at school, aged 16, playing the German electrician-cum-art-enthusiast Shuppanzigh who turns up to mend the fuse. It's a weird sensation, hearing lines that have lain dormant in your memory, unvisited and festering like a neglected elderly relative in a condemned care home, for over forty years. The words blink and open their eyes with vague recognition, then it all comes rushing back. 'Miss Laughingly-Known-As and her Daddy-pegs'. 'Some neighbour monsters, monster neighbours'. 'You old slyboots'. On the way home from the Pilch someone was playing 'Dark Side of the Moon' into the warm evening from a window on Holywell Street, and my unexpected time travel back to my teens was complete.

But there were differences. For one thing, Vita Hamilton's production is about a million times better than the one Mr Lepoidevin wrung out of his reluctant conscripts in 1979. This group of top Oxford actors wrestle every laugh from the fiendishly complex choreography with style, impeccable timing and tongues impishly in cheek at the outdated unwokeishness of it all. Harold Gorringe, next-door neighbour of the less-than-heroic central figure Brindsley, was originally created as a stock, mincing 'poofter', but in Rob Wolfrey's hands he becomes a gay icon, without losing even a smidgeon of the comedy. Clea, Brindsley's ex ex machina (Catty Clare), is now powered by righteous rage at his fickle philandering. Brindsley himself, rather than the standard put-upon innocent at the heart of the melee, is now clearly the oleaginous author of his own demise. And Shuppanzigh - well, I am honoured to concede the role to the ever-brilliant Will Shackleton, who hardly breaks sweat in delivering the ideal German refugee electrician. I've waited decades to hear those lines performed properly. Another one off the bucket list.

Farce is one of the hardest things to get right on stage. When it works properly it's like a marriage of ballet and drama. As one character lights a match another must be there to blow it out, without a pause in movement, and all while delivering lines of unbroken conversation. At its best, the impact is thrilling as well as funny. And you know when it's gone well, because by the end the cast looks relieved, sweaty, exhausted and slightly stunned that they've actually got through it unscathed. That's what happens in this production, and last night the audience rose as one, lifted from their seats by the artificial, inconsequential perfection of pure slapstick.

This being Shaffer, there's method in the madness. The theme is deception, and Brindsley's efforts to keep his friends and fiancee metaphorically in the dark take on concrete proportions in the blackout that descends on him like an avenging angel. Despite all the hilarity, there is an intelligence at work here that lifts Black Comedy from being just another bedroom farce. It deconstructs the conventions of theatre itself, rather than using them to reinforce ancient stereotypes. By enabling us to see in the dark, Shaffer exposes a lot more than Brindsley's shenanigans: he sheds a very 1965 light on a new era of dramatic experimentation, and his stock characters, with one foot in the 1920s, are rocked to their foundations by it.

Black Comedy is traditionally shown as a double-bill with The White Liars, and this production is no exception, with White Liars going first. One exciting innovation is that there is no pause, not even half a second, separating the two plays. Black Comedy charges in like the final movement of Beethoven's Ninth, sweeping the previous music aside in its hunger to grab the limelight.

And in fairness, The White Liars is by far the inferior piece. It's a one-acter about a seaside fortune-teller (again German) who uncovers a love triangle involving some clients, which reveals more than any of them suspected. Although thematically linked to Black Comedy with its focus on deception, it's different in almost every other way. It's static and introspective. Characters spend time peeling away layers of truth rather than catching telephone cords in their groin.

The cast members give White Liars the same high-quality treatment, but it is just a warm-up for the main event. Like a support act for a top band, it feels somewhat unnecessary: there to fill the evening rather than add to it. On a hot June night I would rather go straight to the intravenous adrenaline shot of Black Comedy than let the alcohol swab of White Liars soften my skin.