Rebecca Lenkiewicz wrote her play set in Sligo before visiting the county. She tells Mary Russell  why an Irish setting was appealing.

Rebecca Lenkiewicz, whose play The Night Season is set in Ireland and is currently showing at London's National Theatre, had a happy if unorthodox childhood - plenty of father figures and half-siblings but with the same mother always there for her. She takes her surname from one her mother's husbands - his eccentricity was only truly revealed when the embalmed body of a tramp he had befriended was found in his studio in Plymouth after his death.

Lenkiewicz did well at her school, Plymouth High, taking all the usual A levels before going on to Kent University where she studied English and film. This was followed by a short stint at film school in Moscow, until her time there was terminated by Yeltsin's coup. She returned to England to train at the Central School for Speech and Drama from where she landed a few parts at the National Theatre. In between, she temped and handed out programmes at the National Film Theatre in order to earn a living. She even did a bit of table-dancing in Soho when she was 21 years old, which helped her to just about scrape by.

This year, her 35th, is the first when she hasn't had to make ends meet by doing office work. There is the play at the National Theatre, a shared attachment at the Soho Theatre that guarantees her next play will be produced there and a radio play in the pipeline. A good year, then.

Perhaps it is her genial, emotionally secure background that influenced the final scene in The Night Season, in which more or less everyone in the play discovers happiness, dancing in the arms of their beloved.

"Yes," she says in immediate response to my question when we meet in London, "I am an optimist". It's a trait that shows clearly in the play, which tracks a few short episodes in the life of three unmarried sisters in their 20s or 30s who live in Sligo - or 300 miles north-west of Plymouth as the London Times would have it - with their father and the maternal grandmother who bring them up when their mother runs away to London. The grandmother is played by Annette Crosbie with a challenging mix of battiness and astuteness. The father (David Bradley) is an emaciated romantic, looking not unlike Richard Harris on a good day. All three actors who play the parts of the sisters, Sarah Jane Drummey, Susan Lynch and Justine Mitchell, though London-based, have worked in Ireland.

It is into the sisters' apparently humdrum lives that an English actor walks, to work on a play about Maud Gonne and Yeats. The grandmother takes a shine to him and he is gracious enough to slow-dance with her. The middle sister beds him, the oldest one goes to London for what turns out to be a disastrous meeting with the absent mother while the youngest - let's call her Cordelia for obvious reasons though in the play she is called Maud - sees to it that the father has everything he needs, most importantly a fag in his mouth and a glass of whiskey in his hand. Eating, he maintains, is a waste of time. His tersely-written lines define him. When he returns from a drunken night out with blood all over him, one of the daughters is solicitous: "Have you been in a fight?" she asks. "Since the day I was born," he replies.

Maud has a boyfriend who has two failings: he can only have sex in the dark because he doesn't like taking his clothes off and his life's ambition is to go to Moscow. Inevitably, Chekhov is invoked as are so many other writers, their quotes shamelessly flagged within the dialogue, leaving you wishing Lenkiewicz could speak in one voice only - her own.

Although the notion of the family at odds with itself is universal, Lenkiewicz chose to set her play in Ireland for one main reason: "I wanted the dialogue to be lyrical and Irish people seem to be able to talk like that without sounding flowery." She has never lived in Ireland, but once had an Irish boyfriend. She has also worked as a tour guide taking American tourists around the Ring of Kerry. To celebrate the acceptance of her play by the National Theatre, she treated herself to a few days in Dublin, including a visit to the Abbey to see Aristocrats.

It was only after she'd written The Night Season that she and director Lucy Bailey visited Sligo. "I had to see if I'd got the accents and speech patterns right and we also wanted to look at things like how people dressed." Apart from a few English-isms - "he was stood there", "she was sat", etc - the dialogue rolls along comfortably, liberally peppered with quotes from Yeats, Kerouac and the Bible.

"Originally, I wanted to write a play about the love affair between Maud Gonne and Yeats, but the characters took over.

"Now I'm a bit worried about the reception it will get because it's romantic." And indeed it is, unfashionably so, which is part of its charm, with songs from the shows coming in on cue whenever Lily, the grandmother, gets her way. Fred Astaire and Ginger Rogers are her favourites, something she shares with Lenkiewicz herself.

There is an occasional studentish, shoe-string feel to the production with the cast moving props about and the sound system occasionally sounding not quite right in an auditorium as small as the Cottesloe.

Nevertheless, the London newspapers were kind. "It's quite déjà vu, isn't it?" said the critic from the Independent during the interval. "Vague. Irish whimsy," wrote Michael Billington in the Guardian, although he also praised and delighted in its blitheness and humour as did the audience who laughed along with obvious enjoyment.

The reviews will have pleased Lenkiewicz. Her writing career is progressing well. Soho, her first play - based on her own table-dancing experiences - was performed at the Edinburgh Fringe Festival four years ago, before being taken up by the British Council which toured it in Israel. There has already been interest expressed in The Night Season by Germany and Israel.

Her next play, to be produced by the Soho Theatre, is about the underbelly of London's art world, the arena in which her brother works, making him her main source of information. There is also the radio play to be written for the BBC, an exercise that took her by surprise: "I'd thought writing for radio would be easy but it's not."

The Night Season is showing at the National Theatre in London until November 17th. The text of The Night Season is published by Faber at £8.99