1 Why did you decide to make a film about a terminal illness?
I came back to New Zealand after 13 years making reality TV in the UK and US hungry to take on my first feature. Within days I was at the gym when a mutual friend pointed out a woman having a leaving do because she'd just been diagnosed with motor neuron disease and given two years to live. She looked like she was off to a resort in Bali. I thought, "This woman is not going to be your everyday terminal patient." I knew doctors call MND the "creeping death". Your brain is the last thing to go, so it's like you watch yourself dying. I was morbidly fascinated with what that meant.
2 What did Margaret and her husband, Stephen, expect to get out of the film?
My opening gambit was that we'd make an aide memoire for their daughter Imogen, who was 10. They were right up for it, which was a dream come true for an observational filmmaker. I filmed them once a week for about an hour, mostly in Margaret's bedroom which became ground zero for her caring and philosophising. We became really good friends. As a filmmaker you're looking for drama so I'd go more frequently when she was in hospital or hospice because she hated those places with a passion. Having a terminal illness didn't bother her as much as being institutionalised.
3 After four years of filming, how did you edit all that footage down to an 80-minute feature?
With 120 hours of footage I did get overwhelmed so I called the film school for help. They offered me a fresh graduate who ended up working on it for four years.
4 You could have edited the film in many different ways. Why did you tell the story you did?
At the start it was going to be about Margaret but it turned out to be more about her husband, Stephen, who emerges as the unlikely hero. The beauty of observational documentary is that you probably don't know what you've got until years after you've shot it. Being unpaid, we had time to craft the right story.
5 So as well as being about MND, it's also about what it's like being a carer?
Yes, the art of caring is celebrated in all its horrors and joys. There are 800 new carers in New Zealand every year and like Stephen they're struggling. They want to give their loved one quality of life at home but it comes at a personal cost. Most of us don't see that physical and mental toll. The Kiwi psyche is that you just soldier on. With our ageing population we have a tsunami moment coming and we're not prepared. People like me are in the sandwich generation. I'm caring for two little children and my mother who's got dementia. We need to think about who is going to do the caring and at what level?
6 Did the family ever ask you to turn the camera off?
Even in moments of conflict that never happened. I had to be sensitive to Imogen's needs due to her young age. Thankfully she gave the film her blessing when she turned 16 this year - otherwise it would have been shelved. She's grown up in a confessional online world. Young people are more comfortable with this vernacular.
7 You made lots of reality TV in Britain. What's the worst thing you did to get a story?
Filming a TV series called Mums on Strike, I had to make dads seem incapable of looking after their kids even when they weren't. At one point I put a child's Weet-Bix on the ground when the dad had his back turned and the child got accused. Yes, I did three Hail Marys but I got a good shot. I did what I had to do to pay the rent in London. After that I was lucky to get a job for the BBC making a TV series about the clergy in York Minster. It rated really well and opened up my eyes to a gentler, more humane way of presenting the human condition.
8 The final two weeks of Margaret's life are not in the film. Why?
At the end I wasn't being invited over. I don't think anybody was. I could have pushed it but it just didn't feel right. The Margaret I loved had already gone. She could no longer communicate and had none of her faculties any more. I wonder if she'd had the option of assisted dying if she would have taken it in those last two weeks. I think having the choice would have empowered her.
9 Are you religious?
No but I'm fascinated by the evangelical Christianity Margaret and Stephen belong to. I genuinely think it was a massive comfort for them. They had such strong support from their church community - their house was like Victoria Station at times.
10 All three sessions of the film sold out at the Film Festival. Who would want to see it?
Yes, who would want to see a harrowing, confronting film about the art of caring and dying? But we show the light with the dark. I call it "the ultimate grown-up love story" because there was so much love in that room. There were rows, there was urine and faeces, but essentially there was love. I had a man in gumboots and stubbies come up to me and say, "I'm a cynical man but your film moved me".
11 What was your childhood like?
I was born in London and grew up in the Bay of Islands. Mum's an artist and there's a big single parent artist community there. Seeing the Seven Up documentary series on TV was my lightbulb moment. I studied film at AUT and went to London where I met my husband, Graham McTavish. We went to LA to pursue his acting career and moved to Wellington when he got a job as a dwarf on The Hobbit.
12 How did you juggle motherhood with this film?
One of the reasons I chose this project was that it would fit around family. I carried my daughter in a front pack for a lot of it, providing grief for my sound mixer with the amount of noise she made. The whole reason I had a second child was because Margaret told me to. I found myself doing pretty much whatever she said. I fell in love with her and when she said, "I think you should call your daughter Hope," I did.
• Where There is Life, Academy Cinema from Oct 28. 6pm session includes Q&A with Gwen Isaac. Also Bridgeway Northcote from Nov 9 and Monterey Howick from Nov 10. For screenings nationwide www.wherethereislifemovie.com