PREMIERING at the Fringe next month is Once In A Generation, a play set on the night of September 18, 2014, the date of the first referendum on Scottish independence.

Brought to Edinburgh by Glasgow-based theatre company Sandstone City Theatre, it sees marital harmony under strain as enthusiastic Yes voter Mary tries to convince her husband Dave of the case for Scottish self-governance.

Swept up by the optimism of the campaign for change, Mary has, according to offshore worker Dave, “changed”.

READ MORE: Here's your guide to the Traverse's Fringe programme

“Dave tells Mary she’s changed more than a few times in the play,” says writer-director Julie A Calderwood. “But she has changed, that’s the thing. They’ve gone in different directions.”

The National:

Photograph: Francis Lopez

When Calderwood shared an early draft of the play, she found that the experience of being at odds politically with a relation or significant other was very common among her friends and peers.

“Everybody had at least one experience of a family member or friend who felt completely differently to what they did, and there was the question of whether that relationship would pan out,” she says. “The play does address that, whether Mary and Dave will get through this with their marriage intact.”

There is hope though. Despite being at at loggerheads in their living room, the pair are not political opposites. Dave, played by William Speirs, is no arch-Unionist. He’s more of an old-school leftist, says Calderwood; someone who holds out for those few times Scotland gets governed by the party it actually votes for; someone who would not describe himself as a “nationalist”.

“He does care about politics but he shies away from a lot of things that his wife feels very political about,” says Calderwood of Mary, played by Anne-Marie Feeney. “So many people were politically awakened at the time and Mary is definitely one of them. She got very, very actively involved in everything that has happened in the two years leading up to it, whereas Dave is very grounded, very cautious.”

Mary does meet her match in Campbell, a zealous last-minute Better Together pamphleteer hoping to doorstep any stragglers. Though Dave has already cast his vote, Mary and Campbell fight for his conscience. It’s a tussle many voters experienced themselves too, says Calderwood.

The National:

Photograph: Francis Lopez

“You had your avid Yes voter and your avid No voter, for whatever reasons. But there were whole swathes of people in the middle who really didn’t know right up to the last minute how they were going to vote. I did wonder how these people now feel.”

Like Mary, Calderwood “felt terrible” when the result didn’t go as she’d hoped. It took at least a couple of years before some in the Yes community, she says, were able to begin looking back on the period.

However, Once In A Generation is not a play for embittered Yes voters to tell others “I told you so”. Instead, Calderwood says, it’s a play “for everybody” which remains a work-in-progress continually responding to audience feedback. She hopes this Fringe run, which follows a handful of dates in May at Glasgow’s Flying Duck, will be followed by dates across Scotland.

Lightning fast turn-around times at the Fringe mean there will be no time for post-show chats at these dates, and audiences will be encouraged to take part in the wider discussion via social media.

“This happened to everyone across the board,” says Calderwood. “It was emotional for everyone. When everyone wrapped the whole thing up the next day, it was thought that the status quo had won out.”

She adds: “Some people were delighted about it, and some people, like myself, were devastated about it. We didn’t want the status quo. But there is no such thing as the status quo. It turns out we were all robbed.”

When people are not true to their word, when prime ministers call a referendum to settle an internal party dispute, when the democratic will of a nation is ignored by its more powerful neighbour, anything can happen. And since 2014, it has.

“There were many reasonable reasons why someone might have been cautious in 2014,” says Calderwood. “No voters thought they were doing the right thing, just as Yes voters did. They had no idea things would change.”

Still smarting from 2014, the Brexit vote in 2016 left Calderwood stunned, she says. When he resigned the next day, David Cameron had betrayed a key argument used by Better Together of Scotland remaining part of a strong United Kingdom in Europe. That he could be heard humming a merry tune after his statement added to the sense of unreality.

The National:

Photograph: Tahmina Ali

“It had been: ‘why leave the Union, when you can lead the union?’” remembers Calderwood. “These things began spinning around my head about what we had been told in 2014. Things like the strong pound and the triple A credit rating and how much we were supposedly valued.”

If the Brexit vote inspired her to write Once In A Generation, the fallout since has made Calderwood’s play vital for 2018. Rather than being showered with dubious-sounding “love bombs”, Scotland has been treated with special contempt by the Tory Government recently, its representatives ignored, its parliament subjected to a power grab.

But entirely contained within the hours of the 2014 vote, Once In a Generation’s characters do not have the benefit of hindsight. Only in the final few moments of the play is Dave allowed to see how the following years unfold.

“I think a Yes voter from 2014 is going to feel justified, they’re going to feel angry, they’re going to feel galvanised,” says Calderwood. “But I’m hoping that the play will be food for thought for those who did vote No and for them to say, ‘That was then, and this is now, and it’s OK that I voted No in 2014.’

READ MORE: George Square to be celebrated as Glasgow's civic heart

“Things have changed and we were fed a lot of lines that haven’t turned out to be true. A lot of things were said and promised to us which have not been provided.”

Calderwood adds: “Hopefully, it will encourage everyone to say, ‘OK, so what are the next steps? What can we do?’ I think that the next year, the next months are going to be pivotal in Scotland’s story, so this is the perfect time to be revisiting 2014.”

August 2 to 10, Laughing Horse @ The Mockingbird, Newington Road, Edinburgh, 4pm, free, non-ticketed.