A year ago Kathleen MacMahon, a granddaughter of Mary Lavin and an aspiring novelist since girlhood, was enjoying her secret writing life while working as a reporter at RTÉ. But such a legacy couldn't remain hidden when she received a huge advance, writes RÓISÍN INGLE

THIS IS HOW it begins. A year ago this month, the novelist and RTÉ reporter Kathleen MacMahon received an unforgettable phone call from London. Her literary agent, Marianne Gunn O’Connor, who had been pitching MacMahon’s debut novel at the annual book fair in the city, called to say the five words every aspiring writer longs to hear: “I just sold your book.”

The novel, a love story about an American ex-banker and an unemployed Irish architect that flourishes by and in the sea around MacMahon’s home village of Sandymount in Dublin, has just been published by Sphere.

The cover of This Is How It Ends describes it as “the story of unexpected, life-changing love”. But this is also the story of an unexpected, life-changing advance. Her work sold for £600,000 (€730,000) in a two-book deal that caused huge excitement in the book world, among MacMahon’s friends and family and, not least, in the RTÉ newsroom.

The morning the deal was announced MacMahon turned up for work as usual. “It was like walking into a big hug,” she says. Her presence was noted by the then managing director of news and current affairs, Ed Mulhall, who joked about being relieved she was there, because several staff members hadn’t turned up. They were all at home, he said, searching for the half-written novels under their beds.

Sipping tea at Bellinter House in Co Meath – the county her grandmother Mary Lavin, the writer, called home – MacMahon says she was amazed at the goodwill that greeted her news. As she went about her job that day strangers beeped their car horns in support. “Everybody was amazed and delighted,” she says. “We had great fun; we went around like headless chickens for a month, saying ‘It’s mad, it’s mad, it’s mad.’ It was entirely unexpected. It was unreal.”

A year on, she is wary of “boring people again” with the tale of the advance, but she acknowledges its value as a good-news story in these grim economic times.

It was actually the second time her agent had been to London in an attempt to sell a novel by MacMahon. The year before, her first book, The Sixth Victim, a novel she says will remain under her bed forever, came close to being sold. “At the time, Marianne was very disappointed and I was very relieved. Because I thought, Oh no, I am going to have to tell people I am writing now. I was looking around the newsroom in terror. It felt like I was going to have to stand up and take off all my clothes.”

The secret writing life of this elegant and eloquent 42-year-old began about eight years ago, when her twin daughters were not yet two. She had wanted to write a book since she was 10, saying that never doing so would have constituted “a failure” in her life. In a way the weight of Lavin’s literary legacy held her back. “I spent a lot of time thinking about writing, but I had to find my own voice. I think if I were doing it 10 years ago I might have been trying to impress others. In my family people wouldn’t just be delighted that you had written a book: they would be saying, ‘But is it any good?’ ”

So, as a challenge to herself, she sat down to write a novel in snatches of time stolen between work and parenthood. She told nobody except her husband, Mark, who wasn’t allowed to mention it.

“He would ask how it was going and I would glare at him . . . Poor Mark,” she says. When it was finished she showed it to him. He read it over a weekend and said, “There’s way worse stuff than that gets published. You should show someone.”

“I liked his response. It was sensible,” she says.

The thought of someone reading her work was “horrifying . . . like jumping off a cliff”. But she bit the bullet, sending a synopsis and some chapters to the book publicist Cormac Kinsella, who sent it on to Gunn O’Connor. Impressed, she took MacMahon on as a client.

When that first book didn’t sell, MacMahon thought she would just go back to her “nice little secret life as a writer”. She had another idea for a book, and Gunn O’Connor, whom she describes as “fiercely loyal, all instinct and heart”, said to contact her when she had completed it. So she did, but with a caveat that her agent come back to her only if there was something concrete to report. “I had found it too stressful the first time around,” she says.

Her agent brought the book to London, where editors from various publishing houses read it on Kindles in hotel rooms. One of the editors, Rebecca Saunders from Little, Brown, read it through the night, crying over the last pages and contacting Gunn O’Connor to ask what sum of money would take the book off the table. Her successful pre-emptive bid of £600,000 meant there were a few disgruntled publishers who had hoped for a bidding war.

The pressure, I suggest, must be immense. How is she coping with the weight of expectation? “I am coping fine,” she says. “I am just glad I am this age when it’s happening. I am very solid in my work . . . I don’t care what people think. Well, I do a bit, but I wrote it for me, and I’m happy that what I achieved is so close to what I set out to write.”

There are other reasons for her measured approach that have to do with the kind of perspective gained from personal loss. In late 2010 her mother, Valdi, died after a short illness and just before Christmas last year her aunt Caroline Walsh, the literary editor of The Irish Times, died in tragic circumstances. “My mother was one of the first people to call me a writer, as was Caroline, who was a champion of so many people, including me . . . It’s been heartbreaking,” she says. “I think in contrast to what has been happening in my personal world, losing my mum and my aunt, the book is a good thing. So I’ve got a lot of perspective at the moment. There’s been an awful lot of sadness for us as a family, and this is such a positive thing in all our lives.”

It’s interesting, she says, that when the book was almost finished, some sad events occurred in her life that echoed those in the book. “Without wanting to give away the ending, it was very strange,” she says. “I’d made it all up, and then something quite similar happened in my own life. I was really astounded by how close I was to getting it right. I don’t think it’s creepy or coincidence. I just think if you imagine it well enough that’s what happens. I think it goes to show that the wells you are drawing from are deep.”

Like MacMahon, the book’s central character, Addie, is a keen swimmer, and water is a motif in the book. Addie is also a woman who feels life is passing her by. MacMahon believes we are sometimes too quick to name this kind of disappointment with life as depression. She has known periods of what she prefers to call melancholy herself. “Melancholy has been a factor in my life, not in any debilitating way or in a way that has stopped me doing anything, but it has been there.”

EARLIER IN THE DAY we had visited the ruins of Bective Abbey, which, when MacMahon was growing up, were on the grounds of Abbey Farm, Lavin’s former home. She remembers spending summers there as a child, rambling around the ruin, jumping in the river. Her grandmother, she says, was “a purist. She wore only black cashmere and would have only white flowers in the garden.” Colm Tóibín once described the “beady eye” of Lavin. MacMahon knows what he meant. “You knew you were being watched, you knew she was making judgments about your character. As a family we are all fascinated with figuring people out.”

The centenary of Lavin’s birth is being celebrated this year, and MacMahon often works in a library near her home in which there is a bust of her grandmother. “It’s a strange experience; sometimes it feels as though she is looking at me when I am writing, and I am not sure she approves. A friend of hers did write to me, saying she would have been hopping at the size of the advance.”

Without dismissing the money, she says the real achievement for her has been in realising her girlhood dream of becoming a writer. “I used to wonder sometimes if what I was doing was really self-indulgent, writing just for my own sake, wondering if it was a sunny day should I take the kids to the park instead.” These days when she sits down to write – she is stuck into another book – it feels different. “I am being paid for it now, which does give you great confidence.”

How has she been spending the first few instalments? She admits to purchasing some clothes that in normal circumstances she would have waited to buy in the sales. She is also more flathúileach about “small luxuries” these days.

“I buy firelogs now. I would have been much too mean to buy them before,” she says. “I’m not really a spender – and anyway, until the book was out it felt like buying baby clothes before the baby is born.” She is on leave of absence from RTÉ and will decide in September whether she will return to the broadcaster.

MacMahon reads widely, and mentions Anne Tyler, William Trevor, John Irving and Ian Rankin as favourites. She has little time for literary snobbery. “I’ve had people asking me, ‘Is your book a literary novel?’ Or another way they ask is, ‘What kind of book is this?’

The pigeonholing of authors and books is alive and well. I think it’s odd. I don’t think my book fits into any category or that good writing fits into any category.”

MacMahon says what she set out to do was write a book “that was readable but that had substance”. It has been sold in 25 countries. “Each country is a separate vote of confidence in the book, which is great.”

“I was in London to meet some publishing people recently, and I remember barrelling across London in a taxi, going to the Little, Brown offices. I was thinking, If my 20-year-old self could see me now, she would be really quite pleased at how things have turned out. It’s a lifelong ambition that has been realised. I don’t feel I’ve arrived. I feel as though I am starting out on a new adventure, and I hope to be doing this for a long time.”

Kathleen MacMahon will read a story by Mary Lavin at the Cúirt literary festival in Galway today