I'M standing at a lectern on the stage of the Traverse Theatre in Edinburgh, declaiming, in what I hear as an increasingly pompous voice, the sort of right-wing platitudes I usually abhor.

With the entire audience braying so I have to speak over them, the man opposite is firing back retorts of equally schoolboyish one-upmanship. Sporting a suit I'd like to think gave me the air of a European arts mandarin but is probably more Jeremy Kyle, I find myself becoming the ultimate Tory boy. "My God," I wonder, hearing my decidedly non-Etonian voice rise and fall, "how did I get here?"

I'm appearing in Demos, a new verbatim play by Tim Price and John Bywater, which takes as-it-happened accounts from two very different manifestations of democracy and turns them into mass participatory spectacle. The first, Sort Your S*** Out People, is taken from the minutes of the daily General Assembly of the Occupy Movement while camped outside St Paul's Cathedral in December 2011.

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The second, in which I'm somewhat bizarrely playing UK Prime Minister David Cameron, is taken from Hansard's record of Prime Minister's Question Time the day after the Occupy meeting.

Demos is the climax of Write Here, a week- long festival of play readings, talks and workshops by writers old and new. The idea of Demos is to explore what democracy means to different groups of people. The audience has been asked to bring along woolly hats and true-blue ties in order to look the part, and are given copies of the script so they can play assorted Occupiers in the first play, and MPs in the second.

Part of the investigation is to mix up the casting. Which is how a critic, usually on the other side of the footlights, has ended up alongside professional actors James Mackenzie, who plays Labour leader Ed Miliband, and Kirstin Murray, who plays the Speaker of the House in the second play and lead Occupier Saskia in the first. I studied drama and even carried a spear in the Scottish Theatre Company's famed production of Ane Satyre of the Thrie Estaites, so it's no big deal, I reckon. All those people who reckon theatre critics are failed actors will now have to eat their words.

On the day of the performance, however, it's a bit more nerve-wracking than that. This hits home when I'm sitting in the Traverse bar with Hamish Pirie, the theatre's new associate director who's overseeing Demos. I'm feeling guilty that I'm not chained to my computer banging out copy for The Herald as I usually would on a Tuesday afternoon. Then I'm called for rehearsal, and follow the entire Traverse staff into the theatre. I wasn't expecting this. I thought it would just be me, the director and actors, but these are people I normally request tickets from. What are they doing here? They can't see me make a fool of myself.

Of course the Traverse staff are standing in for the audience, and read in the lines of the Occupiers and MPs. We go through the second play, and, after initial hesitance, I begin to relish Cameron's lines, which in some ways are as subtle as Pinter or Mamet, turning on an emotional pin mid-sentence. One minute Cameron is giving sincere pre-Christmas sympathies to the families of fallen soldiers in Afghanistan, the next he and Miliband are tearing yah-boo chunks out of each other in increasingly pathetic displays of playground antics.

ON the night itself, suited and booted and with 100 audience members playing MPs, the adrenalin kicks in even more, and I hear myself sounding even more pompous than I did at the read-through. And, oh, the power! When I raise my voice, the unscripted booing stops. I could make a panto villain yet, I think, as I revel in every piece of Tory claptrap I'm spouting. As a lifelong wet liberal lefty with occasional flashes of revolutionary zeal, this is rather worrying.

But Demos has clearly tapped into something, and it isn't alone in its exploration of big ideas. This week, the Traverse hosts the Arches Platform 18 double bill of Thatcher's Children and BEATS, while the first of Oran Mor's Arab Spring season of plays, Could you Please Look At The Camera, has also just transferred here. A few weeks ago in Glasgow there was a four-hour unedited reading of transcripts from the Guantanamo inquiry presented by Arika at the CCA. On May Day, the National Theatre of Scotland's Five Minute Theatre season is based on the theme of protest.

Suddenly politics is everywhere in the theatre. There's clearly something happening here that's not just about power, but about people power. By playing David Cameron, I've just had a taste of just how appealing and addictive that power can be.

"I'd vote for you," someone tells me in the bar afterwards. I wouldn't.