The king-in-waiting gets the Shakespearean treatment at Festival Theatre

“Charles is someone who's been waiting all his life,” says Bartlett, “and I was interested in what might happen if there was an accession, with all the contradictions that might entail, because protocol dictates that the Queen has to remain neutral about things and stay silent, but we know Charles' temperament, and we know he has opinions on things.”

Such opinions and seeming eccentricities have been a gift to Bartlett.

“I'd wanted to write about the royal family for a long time,” he says. “A lot of dramatists are drawn to them, including Shakespeare, because, as is clear from Shakespeare's history plays, if you write about a person, then you write about a country. The trap of then trying to write something using that brilliant Shakespearian archetype of a five-act form is that you're immediately setting yourself up to be compared to the greatest English writer ever, but that five-act form is the best way of doing it.”

As such a serious approach suggests, Bartlett's play isn't a piece of over-simplified republican agit-prop.

“The play is written from a very sincere place,” he says. “I wanted to find out the intentions of public figures. It's not cheap satire. Something like that could sustain a sketch, but not a full play. I wanted to explore public roles rather than attack them. I think it's totally legitimate to write about them in this way, in a way that's a contrast to all the cruelty and snark in the world.

“I also think it's important that Charles takes a stand on issues and has principles. Considering the intrusion into his life by the press, for him to support press freedom goes against expectations. It's like when the Chinese president was over, Charles didn't go to the dinner, and gave no excuse. His office was asked and all they said was no comment. That's the Charles of the play, someone who's willing to have principles and will kick up a fuss.”

One of the major intrusions into Charles' life was the saga surrounding his marriage to Diana Spencer, the aftermath following their break-up and the Princess' subsequent untimely death in a car crash in 1997. Diana duly makes an appearance in Bartlett's play as a ghost.

“It's very hard not to tell the story of Charles without her presence,” Bartlett points out. “But the ghost is like a Shakespearian ghost. It's not meant to be spooky. It has a psychology and a purpose.

Born in Oxford in 1980, Bartlett became writer in residence at the Royal Court Theatre in London following his acclaimed radio play, Not Talking. While at the Royal Court in 2007, his play, My Child, was premiered, while the following year, Edinburgh Festival Fringe regulars, nabokov, opened another work, Artefacts, at the Bush.

Bartlett first collaborated with Goold in 2010 on the National Theatre's production of Earthquakes. Bartlett's later play, Love, Love, Love, toured to the Citizens Theatre in Glasgow, as did his contemporary adaptation of Medea, starring Rachael Stirling in the title role. While Bartlett also adapted Chariots of Fire for the stage, more recently he has been noted for his work on TV drama, Doctor Foster, which starred Suranne Jones and was executive produced by Roanna Benn, who previously directed work with 7:84 Scotland.

With Doctor Foster just recommissioned for a second series, Bartlett is clearly relishing his move into the mainstream as much as Prince Charles might if finally crowned king.

“As a writer it's fantastic to walk into a shop and hear people talking about something you've written,” Bartlett says. “There's no better validation.”

To keep King Charles III current, Bartlett has had to keep one eye on the royal family's own ever changing soap opera.

“They have babies, get married and things change,” he says, “so because in the play we're dealing with the royal family as they are on that particular day, I keep on having to rewrite it as things happen. Even things like Harry growing a beard, I put in a line, because audiences will know that happened, and what's fascinating about that is that it reveals how much we keep up with them.”

Would such changes perhaps mean some kind of sequel?

“I hope not,” Bartlett says. “If the royal family stopped having children it would help me enormously, but I kind of hope they'd just stop now altogether.”

Could Bartlett see the royal family being abolished any time in the near future?

“Not so much abolished,” he says, “but I think their influence, power and importance will decrease, and, like in other countries, they'll become something more approachable and more normal, and I think that needs to happen. Although the play doesn't attack them, it doesn't flinch from the fact that the royal family has all this money when people are on benefits, so I think there will come a time when that position will be unsustainable.”

Presuming the royals survive for a while yet, and given that his mother has reigned for sixty-three years now, can Bartlett ever see a time where Charles would take the throne in real life?

“Almost certainly,” he says. “The only thing that would prevent him is if his mother outlived him. He's been waiting his whole life to do it, and his sense of duty would mean he couldn't prevent himself from doing it.”

Despite Bartlett's admiration for the man who would be king, a royal delegation to a performance has yet to take place.

“Charles certainly hasn't seen it,”he says. “I think protocol might prevent that. I'm not sure he'd have such a great time anyway, though I think Harry might enjoy it. We heard rumours that assorted aides or associates have been in, but we just don't know. If the play had been about a politician, something would have happened and someone would have said something, but here, being the royal family, all there's been is a dignified silence. But do feel free to call them. I'd be fascinated to know what they thought.”

King Charles III, Festival Theatre, Edinburgh, November 16-21.

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