Succession is never easy.

Just ask Laurie Sansom, who took over as artistic director of the National Theatre of Scotland in 2013 after his predecessor and the company's founding director Vicky Featherstone left to take over the Royal Court in London. When Sansom's appointment was made in 2012, questions were raised in some quarters regarding his appropriateness for the job.

This appeared to have little to do with the Kent-born director's experience, both in the rehearsal room directing more than 20 new plays as a trainee director at the Stephen Joseph Theatre in the Round in Scarborough, or else running the Royal and Derngate Theatre in Northampton for six years. This included a hit production of the stage adaptation of Muriel Spark's Edinburgh-set novel, The Prime Of Miss Jean Brodie, which played throughout the Edinburgh Festival Fringe in 2009.

Despite such a pedigree, Sansom was seen by some to be the latest in a long line of people from outside Scotland to be appointed to senior arts posts. Featherstone and her associate director John Tiffany had faced similar criticisms, despite respectively commissioning and directing Black Watch, Gregory Burke's dramatic investigation of life during and after wartime for the Fife-based regiment. Black Watch toured the world and arguably changed Scottish theatre forever. While emanating from a minority, some comments had been bruising.

Sansom remained quietly diplomatic in his response, and the comments died down as he got on with the job he was hired to do. Now, however, after developing his programme behind the scenes for 15 months, he is about to break cover with what is probably the biggest show of his career so far.

The James Plays is a trilogy of brand new history plays by Rona Munro which focus on the lives and loves of three generations of 15th-century Scottish kings. With a cast of 18 featuring Blythe Duff and, in something of a coup, Sofie Grabol, star of Danish TV drama The Killing, as Queen Margaret in the third instalment, The James Plays were inherited by Sansom from Featherstone, who commissioned them.

It was Sansom, however, who brokered this ambitious co-production between the National Theatre of Scotland and the seemingly newly christened National Theatre of Great Britain to become what is now the flagship of this year's Edinburgh International Festival theatre programme. While by no means referendum plays, the appearance of the James Plays in the Scottish Government's Homecoming year will nevertheless be seen as significant. For Sansom, however, it was never a done deal.

"The first artist I met when I first came up for my initial acclimatisation with the company for a couple of weeks was Rona," he says of his introduction to The James Plays. "She was finishing off the first draft of the plays, and we talked about them. They sounded fascinating, and right up my street as a director. But I also knew that ... the company had already invested quite a lot of money, and Rona had invested a huge amount of her time. And your heart kind of sinks a little when these three huge scripts arrive on your desk, because you're just thinking 'Please let them be good'."

As soon as Sansom started reading them, however, he was smitten.

"I was thrilled by their contemporary feel, the lyricism and the theatrical possibilities," he says. "By the time I'd got to end of the first act of James I, which is an extraordinary piece of writing, I knew the company had to do them this year. By the time I'd finished all three of them, I thought that if I could do anything, it was to try and get them on together with the same company in the same year."

Sansom has spent the last year developing the plays with Munro, workshopping them with actors in between forming alliances, first with Edinburgh International Festival, then with the National Theatre in London, where the production will transfer after Edinburgh.

Talking during a late afternoon lunch-break from technical rehearsals in Birmingham after what has been an epic 14-week rehearsal period, Sansom appears remarkably fresh and stress-free.

He may of course be bluffing, because, like it or not, The James Plays will be Sansom's calling card for his tenure at the NTS. Whatever happens later, for a while at least he will be defined by it. The production will be under extra scrutiny, and not just by critics of his appointment. There is the fact too that the NTS hasn't always fared well in its EIF productions. Yet, despite the timing and high profile of The James Plays, Sansom maintains that there has been no political interference from outside.

"If I thought there was any reason for doing these three plays other than the fact that they're brilliant pieces of writing," he says, "I'd be very scared right now. "It could look like we're ticking boxes, but these are the best new plays I've read for a very long time, so I don't feel that pressure, and I haven't felt like it's been hijacked in any way. The only pressure I feel is to do the plays justice."

Neither does Sansom deny that the moment is right for The James Plays.

"If you tell a story about a king, you're simultaneously telling a story about an individual and a nation, and theatre is arguably the best artform for looking at the psychology and the decision-making of an individual in a wider social and historical context, "he says. "So to be looking at this period of largely unknown Scottish history in 2014, when the nation is looking at itself and wondering what kind of country it is and what it could be, is clearly such an exciting opportunity to reflect on cultural identity. With everything that's going on this year, it was too alluring not to do it."

See tomorrow's Sunday Herald for an in-depth interview with actress Sofie Grabol, star of James III: The True Mirror and Danish television series The Killing