Their trilogy of plays by Ireland’s greatest living playwright, Brian Friel, (which opens in Edinburgh today with the acclaimed drama Faith Healer) positively bristles with talented stage artists. This is particularly true of the third and final piece, the Chekhov-inspired Afterplay, in which the fine English actress Frances Barber is directed by leading Irish director Garry Hynes (the woman behind the Druid Synge season, which set the Edinburgh Intenational Festival alight in 2005).

No-one, it seems, is more excited by the prospect than Barber herself. “There were three reasons why I wanted to do this,” she says. “I’ve always wanted to be in a Brian Friel play; I’ve always wanted to work at The Gate; and I’ve always admired Garry Hynes’s work. When the three elements came together, it was just a perfect opportunity.”

It was also a chance for Barber to revisit an old character. In Afterplay she performs the role of Sonya from Chekhov’s Uncle Vanya, a part she played, to many plaudits, in Chichester and London in 1996. The difference is, this time her character is 20 years older. Still carrying the deep pain of her unrequited love for the country doctor Astrov, Sonya meets Andrey (from Chekhov’s Three Sisters) in Moscow as the Russia they knew disappears in the ferment of revolution.

“It’s extraordinary how clever Brian Friel has been,” says the actress, “amalgamating these two characters and inventing, in his imagination, what happens to them 20 years on … When I read Afterplay, I thought it was just so beautiful and the most lyrical, poetic and simple little playlet about loneliness, desperation, sorrow, depression and unrequited love. It’s just an astounding piece. So, I jumped at the chance. It’s also optimistic, in a curious way. Like Beckett can be. That existential view of the world is considered to be nihilistic, but actually it isn’t – it’s uplifting.”

Barber’s enthusiasm for taking the role was fuelled, in part, by the chance to work in Dublin, and particularly at the internationally renowned Gate. The actress has done some TV work for Irish national broadcaster RTE in the past, and she’s played alongside some of Ireland’s finest actors, such as Liam Neeson and Ian McElhinney. Afterplay, however, is her first Irish stage production.

Speaking to me on day two of rehearsals, she finds a subtle difference between theatre-making in Dublin as compared with London. “As far as I can see, it’s exactly the same, except everybody’s friendlier, with a big smile on their face. This morning, for example, I had to go to the dentist, and the doorman in the building couldn’t have been more helpful. In fact, I had to laugh, because he was taking so much time that I thought I was going to miss my appointment. That wouldn’t happen in London; they’d just shove you up to the second floor and you’d have to find it yourself.”

Barber anticipates a fruitful partnership with actor Niall Buggy, who played the role of Andrey in the original Gate production of Afterplay. “He was extraordinary during the first read-through, which made me anxious,” she admits. “But I know Niall, I’ve worked with him before, and he’s the most generous, gorgeous man, so I know we’ll do this hand in hand. What’s lovely for him is re-exploring the play, that’s always a fascinating thing to do.”

Thirteen years on from her acclaimed performance in Uncle Vanya, Barber finds that Friel’s play offers a fascinating development of the character of Sonya. “She discusses, in Brian’s play, the difference between fortitude and courage. You can be courageous, but you will then pine away trying to cope with the disappointments and vicissitudes of life in a way that’s so full of anguish that you can’t carry on. If you muster fortitude, from somewhere in you, then you can carry on. If she falls in love with Andrey, whom she meets in this cafe in Moscow, she might fall apart. But if she goes back to what she knows, she doesn’t expect anything more.”

Sonya’s conscious decision not to have the “courage” to take the risk of falling in love relates, Barber suggests, strongly to the human condition in general. “As Sonya herself says, ‘It’s no way to live your life, is it?’ But I reckon quite a lot of people do live their lives like that. It may not be unrequited love but, rather, it may be that they’re not in a job that satisfies or fulfils them, or they’re in a marriage that’s stale, but there’s no way out because of the economics of the situation. Sonya’s conviction is that you’ve got to carry on.”

There is no dissatisfaction for the actress in her return to Edinburgh. Last seen on the Fringe playing opposite Christian Slater in One Flew Over the Cuckoo’s Nest in 2004, her enthusiasm for Edinburgh and the Festival remains undimmed. “I’ve got a friend coming over especially from LA because I’m in the Festival... I remember, when we were doing Cuckoo’s Nest, Christian Slater saying that he had never been to the Edinburgh Festival before. He just thought it was the most incredible thing he’d ever seen in his life.

“I would defy anybody not to say that. It is the biggest, the boldest festival; it has such an extraordinary range. I’m thrilled to be playing the official Festival. I love Edinburgh, and I’ll have lots of friends there doing stand-up and different kinds of shows at the Traverse and other theatres. I’m so looking forward to it.”

Afterplay is at the King’s Theatre, Edinburgh, August 31-September 5 (not 2); Faith Healer is at the same venue, today-Tuesday (not Monday) and September 2-5 (not 3); The Yalta Game runs August 29-September 5 (not 31, 2, 3). This EIF season of Brian Friel plays by The Gate Theatre is supported by Culture Ireland Visit www.eif.co.uk.