BY any measure, this second decade of the 21st century has been a frantic one for Emma Donoghue – or as frantic as life gets for anyone whose job is filling blank pages with stories.

From the mid-1990s through to the end of the Noughties, the Dublin-born author wrote steadily and doggedly, publishing six novels to quiet acclaim as well as plays, radio dramas and a trio of academic literary studies. She even edited The Mammoth Book Of Lesbian Short Stories.

Then, in 2010, came Room. It tells the story of a young woman, known as Ma, and her son, Jack, borne to the man who snatched Ma off the street seven years earlier. He's referred to simply as Old Nick. Imprisoned in a single room, mother and son create a world in which their meagre surroundings are all that is real, and everything else exists only on television. The novel was inspired by the case of Elizabeth Fritzl, held captive by her own father in the family home at Amstetten in Austria and continually raped by him over a period of 24 years until she was freed in 2008.

Partly because the Fritzl case still had such purchase on the public consciousness at the time, but mostly because of that ineffable magic that sometimes adheres to a story when a novelist puts pen to paper, Room became a million-selling publishing phenomenon. It won the Commonwealth Writer's Prize, was shortlisted for the Man Booker Prize, sailed up the New York Times bestseller list and became a film. Directed by Donoghue's compatriot Lenny Abrahamson, and starring Brie Larson as Ma and nine-year-old Jacob Tremblay as Jack, it was nominated for four Academy Awards. Larson won Best Actress but Donoghue missed out on the Best Adapted Screenplay gong. Still, she got to go to the Oscars.

Now, in a third manifestation, Room is set to become a stage play for the National Theatre of Scotland – this time with songs. It's this project that has brought its amiable, fast-talking author to London from her home in Canada to oversee rehearsals in the company of the show's Scottish director, Cora Bissett. Donoghue has written the script, and the music is by award-winning Scottish singer-songwriter Kathryn Joseph.

“I always had a good feeling that Room would work well on stage because it's a very theatrical premise – the idea of people using their imagination to make a world of fun and pleasure that doesn't really exist,” Donoghue tells me during a break in rehearsals. “But one thing I hadn't thought of was to add music and I would say the songs are the most exciting new element of this production because somehow they fill in those moments when there are things Ma can't say to Jack and, in the second half, that he can't say to her.”

So would she call this version of Room a musical?

“I really wouldn't. My friends keep asking me what the difference is and it's hard to put my finger on. But I would say that whenever you have a musical, whether it's West End or not, you always feel that strong grip of convention – the opening number, the heart-breaking song that will be reprised in the second half etc. These are all strong conventions of the musical and we're not using any of those.”

Nor does Donoghue accept that Room ever had more than the barest of relationships with the Fritzl case.

“For me this has never been a crime story,” she says. “The crime is a helpful device for isolating motherhood and childhood, and the strange little bubble it is [but] I'm really not at all interested in the Josef Fritzls of this world.”

In fact, she thinks, Bissett's stage production will underline the fact.

“As we're watching the mother and child on stage they could be any mother and child in a grotty, tiny flat with limited options and somebody they're scared of. They're living at the mercy of others. They could be in a detention centre, they could be trafficked. There are so many situations in which people are un-free and in getting away from the burden of being naturalistic, it has really brought out the universality in the story.”

So Room, at its core, is about “a mother and child playing games in the dark,” she says. They have “limited resources and no freedom. But they've got imagination and they've got love. So that's the essential story and it's the same in all three forms”.

Despite having always thought Room would make a great play, Donoghue had previously resisted all overtures from producers. These had included offers from both the commercial and the avant garde end of the theatrical spectrum. Nothing felt right until she received the proposal from Bissett, whose previous works as director have included Roadkill (about sex trafficking), Grit (a high-energy re-telling of the life of musician Martyn Bennett) and Glasgow Girls (a musical about the real-life Drumchapel schoolgirls who battled the authorities over the treatment of asylum seekers).

“Cora wrote to me and her reputation seemed such a wonderful combination of being extremely experimental – I mean talk about taking risks! – but also very warm and political and passionate. So she didn't have a coldly avant garde feel. She seemed like somebody who really cared, but who cared most of all about making really excellent theatre.”

NOW 47, Donoghue has been a Canadian citizen since 2004 having moved to the country in 1998 with her partner, Christine Roulston, who she met while both were studying at Cambridge University. They live in London, Ontario, where Roulston is a professor of French and Women's Studies at Western University, and they have two children together: 13-year-old Finn (who's with Donoghue in London) and nine-year-old Una.

It was Finn who was the model for Jack in Room, to the extent that Donoghue even tried rolling him up in a rug in the same way Ma does with Jack. Today, Finn and his mother have been watching one of the three boys playing Jack in the NTS production – they are Darmani Eboji, Taye Kassim Junaid-Evans and Harrison Wilding – go through the same ordeal. Donoghue found the experience amusing, if a little weird. She doesn't say what Finn thought.

I ask her if, had her daughter been born first, she would have made Jack a girl.

“I do remember thinking – OK, should it be a girl?” she replies. “Then I thought, 'No', because I want the mother and son between them to represent the whole human race, so we need both genders there. You need Jack's wonderful, playful boyishness to set against the horrible, patriarchal masculinity of Old Nick because otherwise it would seem like a men against women story, which it so isn't. So having a mother and a boy, it brings out the feeling that this pair are starting the whole world again from scratch – they contain all the best elements of being human, and they can make a world in one grotty little 10-foot square.”

Donoghue's own children continue to inspire their mother. Earlier this month she published her first children's book, The Lotterys Plus One, aimed at children in the eight to 12 age group and telling the story of a sprawling family unit made up of two gay parents, two lesbian parents, seven kids – one of them nine-year-old heroine Sumac Lottery – and five pets. There's also a grandfather with dementia who joins the band.

“I have lines from my kids on every page of it,” Donoghue laughs. “They're starting to feel more and more ownership of my work.” Mind you, she adds: “I use my children strategically. I don't just write about them.”

The Lotterys Plus One is the first in a series Donoghue has planned. She's currently writing the second instalment. It's a project she has long wanted to undertake, though she's aware that in light of what she calls “the new sinister political developments” – she means Trump, Brexit, Le Pen and all that – now is a particularly appropriate time.

“Lighting a little candle in the form of a family who are absolutely diverse and flourishing feels like a really important thing to do, because kids are not naturally prejudiced, it only kicks in later when they pick it up from the adults. So helping to communicate to child readers that a family like the one I'm writing about can utterly flourish and look after all its members is a crucial political thing to do.”

Talking of political acts, the man who beat Donoghue to the Man Booker Prize in 2010 – British journalist and author Howard Jacobson – has been the first out of the blocks with a novel about Donald Trump. His is a satire called, appropriately enough, Pussy. Does Donoghue foresee further “pushback” from the creative community – and if so would she participate?

“I prefer to do my cultural commentary at a bit more of a remove,” she says. “I'm not comfortable working in the moment about things that are happening now. I'm more comfortable writing about several centuries ago, or at arm's length from fact, as in Room.”

That doesn't mean “pushback” isn't required. Through measuring her own life's journey “from me as a miserable, closeted lesbian in 1980s Ireland through to today [when] I'm so celebrated in Ireland and so treasured as an Irish writer”, Donoghue can chart the advances in gay rights. But she's under no illusions that the values of diversity and tolerance she holds dear are under attack on several fronts from the rise of the right.

“I have to say, the trend politics has taken in the last year, both in Europe, the British Isles and in the States, it makes me think that the good times could be over … Sometimes I think we're like Weimar Germany, you know, partying in the cabarets just before the Gestapo arrive.”

Whatever happens, she will continue to busy herself writing and, yes, her industriousness may verge on the frantic. She's currently working on several TV projects – adaptations of other writers' works, is all she will reveal – as well as film adaptations of the two novels which followed Room. They are Frog Music, a historical whodunnit set in 1870s San Francisco, also a New York Times bestseller, and The Wonder, about a young girl in 19th-century Ireland who claims to have been living without food for four months. Frog Music is likely to hit the screens first – Keith Allen's film producer wife Alison Owen is behind it – but it's the chance to film in her Irish homeland that seems to set Donoghue's pulse racing.

“My ideal summer,” she laughs, “would be on a film shoot of The Wonder – in some Irish bog.”

Room opens at Theatre Royal Stratford East on May 2, then at Dundee Rep on June 13

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