David Greig wonders if what he has done in his latest play should even be allowed. Technically, he has only adapted a book. His romantic two-hander takes its inspiration from Under Another Sky: Journeys In Roman Britain by the journalist and author Charlotte Higgins. But inspiration is almost all it takes.
Most playwrights would say a book about visiting Roman sites was unadaptable. Under Another Sky is a compelling read, but as Higgins ventures around the country with her partner Matthew, seeking out ancient remains and contemplating how different generations have thought about the past, nothing about it screams theatre. The most dramatic it gets is their campervan struggling to make it to the top of a hill. Not wishing to ruin the engine, she and Matthew get out and walk.
"It came about because it was impossible," says Greig. "I really liked Under Another Sky and thought, 'How would you adapt that?'"
What started as an experimental sketch at the 2019 Edinburgh International Book Festival has flourished into a full-length play. Greig's way in was to turn Charlotte and Matthew into the lead characters, even though Matthew is an almost silent presence in the book and the author herself makes only the occasional first-person interjection – something she does for a very particular reason.
"The whole book is about how historically contingent our relationship with the past is," she says. "When we look at the ways people in previous centuries thought about our Roman past, we can see how dependent it is on their own situation, their own environment, economic and social status. Putting myself in the book was a way of making really obvious that my reaction to the past was equally historically contingent."
Greig has effectively dramatised the writing of the book, rather than the book itself. His play is about a couple discovering love through a shared passion for ancient history. He sees it as a romcom, but pronounces it "Rome com". Or does he mean "roam com"?
Whatever you call it, the play is a work of fiction. Except it is fiction rooted in the lives of two real people.
"I don't know if it should even be legal," says Greig. "It's fiction, but it has got Charlotte's name attached to it and it is sufficiently close not to be able to completely dismiss it. Nobody in their normal life, except Charlotte, has ever had to read something that has, "the end" written at the end of a chapter in their life."
For her part, Higgins is half-bemused, half-delighted by seeing herself – or some imagined version of herself –brought to the stage. In Elizabeth Newman's production in Pitlochry Festival Theatre's outdoor amphitheatre, she will be played by Amelia Donkor, while Matthew will appear in the shape of Keith Macpherson.
"David has created characters called Charlotte and Matthew who are not quite me – and definitely not quite Matthew," she says. "A version of myself is now the object of scrutiny by another creative mind and that is a curious and fascinating position to be in. I can't say it's comfortable. I read the latest draft and my stomach was turning over. It is a gorgeous, charming play, but it is odd becoming someone else's material."
Especially when that material is reshaped for dramatic ends, as Greig confesses: "I am going to say this now: we know that Charlotte is good at deadlines and in my play Charlotte is bad at deadlines."
"It is almost defamatory," says Higgins. "I am unbelievably good at deadlines. I delivered my last book a month early and this evil playwright…"
She breaks off, but behind the teasing, they have much in common. "What David and I share is a fascination with what we're thinking when we think about the deep past. Why do we do it and what do we want to get out of it? David and I have different approaches to this, which are enacted in the way he has created the play."
"The whole play is me trying to argue with Charlotte but I've formed that into dialogue," says Greig. "I hope that somewhere between the two characters, they are exploring all the different ways we look at the past. Can we make a connection with the past and if we can, what are we trying to achieve?"
The staging in Pitlochry's amphitheatre is appropriate. It was here on this stunningly situated stage hidden in the Explorers Garden that Newman presented Greig's Adventures With The Painted People last year. In a kind of mirror image, that play was set in a Perthshire of 86AD that looked forward to today. Under Another Sky is set in modern times and looks backwards into the past.
"Rome is the one bit of history that we always see ourselves in," says Greig. "It's partly because it's an urban culture, a written culture, with baths and all of these things. That means Rome is this odd mirror in the middle of a swamp. Everywhere else you look, you see hessian and axes, whereas here, you say, 'Oh, I can see myself there.' I'm interested in two people reflecting on that."
The exciting news is that after a lockdown spent in a garage in Motherwell, the author's treasured VW campervan – which Greig calls the "only accurately portrayed character" – should be roadworthy enough to make the journey to Pitlochry. "Perhaps it will be hosting the first-night party," laughs Higgins.
Under Another Sky is at Pitlochry Festival Theatre from 10 August until 23 September, www.pitlochryfestivaltheatre.com