Roam Mark Fisher for Scotland On Sunday

In Edinburgh Airport, Ben Harrison sees a child scooting around the check-in area. Everyone else is dutifully lining up in ordered rows, but she is just a slip of a thing and the finer points of airport etiquette are lost on her. Her game is to run headlong into the tensile barriers and make believe she has been knocked out. It’s a flagrant breach of the unwritten rules, but who’s to stop her?

Airport rules are something Harrison has been learning a lot about lately. He has had to figure out all the “invisible boundaries” that demarcate which part is controlled by Customs, which by the Department of Transport and which by Special Branch.

With his colleague, Judith Doherty, he has had to persuade a security-conscious organisation that there is nothing dangerous about staging a play beyond the check-in desks, X-ray machines and passport control officers. Of course, the audience will bring photo ID as well as their tickets, they have had to assure the airport staff.

And they have had to explain that their company, Grid Iron, has performed in a playground, a department store, a derelict building, a cancer hospital and a haunted underground close, so they know all about the logistics of making theatre in unusual places.

Eventually, it was the company’s 10-year track record coupled with the backing of the National Theatre of Scotland that convinced the airport to let Harrison and Doherty have their way. The authorities read the script and the only change they requested was to do with a code word used for abandoned luggage. “They were nervous about that, but it is meant to be a code,” says Harrison, reasonably. “The fact that they agreed in the first place is extraordinarily imaginative.”

The show is called Roam and is based on an idea Harrison has been toying with since 1996. It’s not hard to imagine why this Roam was not built in a day. This morning, the memory of the cavorting girl has caught Harrison’s imagination. When I meet him for breakfast in an Edinburgh café as rehearsals reach their most intense, he’s talking about recreating the image in the show.

“Hopefully that’ll be in it,” he says. “There’s definitely a group of naughty children.”

If it seems odd for him to sound so vague only days before the first night, it’s because of the odd way he has to work. His script is complete and better developed than ever thanks to a two-week workshop earlier in the year.

His multi-national team of actors are well rehearsed, among them the talented John Kazek and Andrew Clark (already making his second National Theatre of Scotland appearance after starring in Home in Dundee). But nothing can fully prepare the director for the unique experience of being in a real-life building with a real-life audience in pursuit.

Thinking on his feet is what he’s good at – as Grid Iron’s countless awards from the Edinburgh Fringe will attest – and it’s in these past few days that crucial creative work takes place.

Drawing on the talents of the St Bride’s over-55s drama group (“They’re great – they just talk about sex the whole time”) and a team of foreign children recently arrived in Edinburgh, he will be turning the airport into the stage for a play that will take place while the final travellers of the day pass through.

“You’ve got to try and hold on to your first experience of going to the site, which is the experience the audience will have,” he explains.

“If you’re there too long, the danger is you stop playing the obvious. If the audience go into a check-in area, you’ve got to use the check-in desks – it’d be crazy not to. So I’m not too worried about having too little time to prepare.”

Last year alone Harrison took 65 flights – a reflection of his standing as a director – and he knows only too well the strictures of airport life. For Roam, he had hoped to have fun changing the signs until he realised how many signs an airport has – and how many permissions he would have to get to change them.

He has, however, been given the freedom to feed new material into the TV monitors, so look out for a few glamorous destinations for which the airport has not previously been known.

“I’m always fascinated by those monitors,” he says. “Alain de Botton talks about going to Heathrow and staring at the monitors – it’s as if the answers are there. It’s such an everyday object and yet the text in it is so exotic – imagine what Bogotá would be like and you could be there in 12 hours.”

Roam, he says, is the company’s most political play to date, a reaction to his experience working in Beirut last year, and in Jordan the year before. He has learnt that for many people in the Arab world, an airport is a place of interrogation and degradation.

“Airports are places where you’re confronted by your national identity,” he says. “I never think of myself as British until I’ve got the document in my hand, standing in Beirut airport hoping it’s going to go well. At the border you’re judged by your flag. People always say they’re very neutral about flags, but they’re sure as hell not.

“If you’re an Arab in Tel Aviv airport it’s the most humiliating space in the world. You have to arrive five hours before your flight – they don’t say that, but they’re always going to try and delay you.”

The play is not stridently polemical, however, and, as we move from check-in to immigrations to baggage reclaim, we will come across just as much about beach towels, bucket holidays and bored businessmen.

“We contrast the very difficult travelling to the very relaxed travelling of a bunch of pensioners going to Malaga,” he says. “At the other end of the age scale are the children who are the anarchists of the airport: ‘Hey, it’s a playground.’ And the opening scene is just a couple saying goodbye.”