For three decades, Alan Gilsenan has been a key figure in Irish cinema. When he started out in the late 1980s, the idea of a national film industry was notional at best, and getting a movie made was well almost impossible. But that didn't stop him making a name for himself in his mid-20s, first with a Becket adaptation, Eh Joe, then with a series of challenging and controversial documentaries.

Since then, his name has become synonymous with quality documentary, but in his latest film, which opens here this week, he returns to his first love - drama. Unless is based on a novel by Carol Shields and stars Catherine Keener as Reta, a successful and happily married Canadian writer who struggles to cope when her grown-up daughter suddenly and inexplicably decides to live homeless on Toronto's wintry streets. It was a project born very close to home.

"I'd heard of Carol Shields' work of course," Gilsenan tells me, "but like a lot of people, I'd thought of her as a woman's writer. Then, one night, my wife passed the book across the bed and said, 'there's a film in this'. Normally I'd just say oh yeah, yeah, yeah and mean to read it and wouldn't get around to it. But I started reading and I was just taken by it straight away. It just seemed like a story for our time, and I was quite struck by it, even though it's a very internal kind of monologue, and the last thing you'd think of filming."

The film's title refers to the fears and doubts that beset even the luckiest souls in the dead of night.

"Carol Shields had quite a charmed life, but yet there's that thing that we all do, of going through life hoping everything's going to be okay, you know, I'll be okay unless I get sick or unless I lose my job, and I think that's what Unless is about. And of course with Carol, the 'unless' thing happened: she had this fabulous family, fabulous husband, gorgeous career, and then she got cancer." Shields died in 2003 at the age of 68, and Unless was her last book.

"When I was in Toronto filming," Gilsenan remembers, "people would ask what are you doing, and I'd tell them, and the only equivalent I can think of here is Seamus Heaney, where people (a) would know her, and (b) love her, and (c) usually had a story about her. She's much loved in that city."

Gilsenan was also blessed in his choice of leading lady. "I was amazed and delighted when Catherine Keener said yes. I think she's a truly great actress, I don't think she's got her acknowledgement in a way, partly because she's a bit of an anarchic figure, she's a wild card. She probably doesn't do what she's told and she probably doesn't do what her agent tells her either.

"We really got on well," he says. "I found her wonderful, I mean challenging and difficult - and I would say that if she was here, but then I think all good actors are - and we had a fantastic time doing it. I was only talking to her the other night, and we were reminiscing, and it was a tough shoot, it was the coldest March in Toronto in 150 years, and the shoot was tight, only 21 days. But she was great, and she had a great influence too, actors love Catherine and really respect her, so the others responded to that."

In the film's most troubling scene, Reta's homeless daughter Norah (Hannah Gross) is sexually abused by a stranger who initially seems avuncular.

"I think that's the only scene that's not in the book," Gilsenan tells me, "and it's there partly because I felt it was almost inevitable for a woman on her own on the streets to have something bad happen to her, and we wanted to reflect the reality of homelessness.

"When we were shooting and Hannah was sitting on the street in minus 35 degrees, you kept thinking what must it be like for the real homeless. While we were there, a young toddler wandered out of the house by accident in the middle of the night and froze to death, and so you realise how harsh that climate is, and so that scene was kind of invented, and it still makes me squirm."

Gilsenan's work in drama and documentary has been widely admired for decades, and his career leaves him well placed to assess the radical transformation the Irish film industry has experienced since the 1980s.

"Huge changes," he says, "I mean when I made my first short film, there were only two short films made in Ireland that year, so if you even finished it, it was kind of a national achievement.

"Now there's probably 2,000 short films made here every year, and you really have that sense that Irish film has come of age, in a way that you couldn't have dreamt of in the 1980s and 1990s. And I think that's great, but I would slightly worry, and I wonder is this an old-fogey thing, that it's become a bit of a production line, and that film has become a little bit straight-jacketed. I don't see too many maverick imaginations out there."

Alan's first love was drama, and his career as a documentary-maker began quite by accident.

"Channel 4 came to me and asked would I like to make a documentary, and to be honest, I didn't really know much about documentary at all at that point."

He learned fast, and in 1988 completed The Road to God's Knows Where, a film charting the stories of young Irish people who'd been forced to emigrate. It won a European Film award, but back home the powers that be were not amused.

"Bord Fáilte condemned it," he recalls, "the IDA came out and publicly condemned it, and I thought that was fantastic. Then it started winning European awards and all sorts of stuff, and I remember maybe a year later being in a pub in Booterstown in South Dublin and the bar was packed and I was trying to order when this guy tipped me on the shoulder. It was the spokesman for the IDA, and he said, 'You know that film of yours did very well!' And it was almost like there were two sides to it: first you made a film that went against the official propaganda of the State, so you were criticised for it, but when it did well, its success made it part of the propaganda."

The film, and the IDA's reaction to it, helped put him on the map, and in TV documentaries like Stories from the Silence and Prophet Songs, he continued to explore the harsh realities of Irish life.

In the 1990s, ITV asked him to work on a series of literary profiles called God Bless America, and one of them focussed on the legendary essayist, screenwriter and novelist Gore Vidal. "I really loved Gore," he tells me, "he was all the things you'd expect, funny, bitchy, gossipy, social, but also, he was just a lovely man. You'd be sitting there over dinner and he'd be saying 'I was talking to Hillary Clinton the other day' or 'I remember the time I was out with Jack Kennedy', dropping names to beat the band, and you'd think, oh this is a star thing, but I noticed when we were shooting that he had exactly the same interest in the guy that was driving the car. He loved people, and he was just great fun."

Is there a film he's fondest of? "No, I'm never happy. If I was honest with you, I'd say I never made a good film, you always think, well the next one now, I'll get it right. There are bits of things I like and films I have affection for - I made a documentary on Roger Casement and I made one on Liam Clancy: they're flawed of course but I'm fond of them."

Does he ever wonder what it would be like to be starting out as an Irish film-maker now? "I think it's kind of frightening these days," he says, "because it's a bear pit, it's ferociously competitive, the colleges around the country are churning out people who want to be film-makers every year, and it's a heartbreakingly difficult thing to do. So on the one hand I can understand people being cautious and clever and trying to play the game, but ultimately I think that what wins through is the people who are authentic and true to themselves and make the thing they want to make. Often I go to the colleges and talk about documentary, and people say, oh I read this story online about this transsexual Buddhist nun in Peru. That might be a great story, but invariably, the best stories are close to you."

He, meanwhile, is ploughing on with new projects.

"I've been writing a couple of new screenplays," he says. "I'm never short of ideas but you never know what's going to get made, and I kind of enjoy that. I've been blessed in that I've been able to keep making things and make what I want, and that's a real privilege. But it is a mad business, and you know if you thought about it for too long, you wouldn't do it."

Indo Review