Mary Pat Kelly is dressed all in black - a smart tunic over flowing pants - and though there is no hint of a wimple or a habit, it is somehow no surprise that she was once a nun; her perfectly made-up face has that almost unnaturally smooth look of many nuns. But once she opens her mouth, the illusion ends. Brimming with stories - of Hollywood, of Martin Scorsese, of the US marines - she is warm, vital and world-wise, if not worldly.
Mary Pat's new novel, Special Intentions, just published, is based on her experiences in the order of the Sisters of Redemption in the US in the 1960s. She joined at the age of 17 after a happy childhood in Chicago and left aged 23, with endless experience of silence and obedience, but little in the ways of the world.
"I really wrote the book to find out why I did become a nun. I was always the little girl who put a towel on her head pretending to be a nun - I really felt it was God's will that I became a nun. I was also a very idealistic 17-year-old - I wanted to change the world and I didn't know where else to do it."
I ask if she has ever regretted her decision: although the book is a very affectionate account of her years as a novice and young nun, full of friendship and belief in her own mission, she was also placed under a lot of strictures that at times came dangerously close to suffocating her.
"I don't think I've ever regretted it, but I have wondered what paths my life would have taken if I hadn't joined the order. Still I've enjoyed my life, and it did get me out of a very narrow way of life. All that was expected of girls where I grew up was that they got married and had children."
She regrets not having children, but points out that the convent cannot be blamed for that as she left when she was 23 years old. "But it took me some time to get back into the dating game."
She has now been married for 10 years to a Tyrone photographer, Martin Sheerin, whom she met while making a documentary on John Hume and the SDLP. From a convent to the world of film and television is not a usual path, but Mary Pat's story is not a usual one.
While still a novice, she decided to do her thesis on film and, lacking books or source material, wrote to a 25-year-old film-maker she had read about in an article. He wrote back - a 17-page letter full of helpful notes, dreams and aspirations. That was Martin Scorsese, the year was 1965, and the pair have been friends ever since.
"I later found out that Marty had trained to be a priest for a few years, so he knew where I was coming from," she laughs.
Mary Pat made the final decision to leave the convent after an exhilarating year spent in a poor, predominantly African-American school in a bad area of Chicago. During the Chicago riots of 1967, she stayed in the school surrounded by burning buildings and, in the chaos and grief after Martin Luther King's death, was spotted sharing a bottle of cola with one of the students.
"I was severely reprimanded. I couldn't believe it - our country was at a crux and I was scolded for drinking Pepsi. That's when I really began to realise that maybe this structure was not for me."
She left and became involved with the civil rights movement - "really another religion" - working as an "urban life adviser" in the same area as the school.
"Can you believe that?" she squawks with laughter. "I didn't even know how to write a cheque!"
It was after a trip to Europe that she decided the arts were what interested her most. She is now an award-winning documentarymaker, but when she first started she worked with Scorsese on festivals and films, studied in New York University, and wrote and produced for TV shows such as Saturday Night Live.
When Scorsese began work on The Last Temptation Of Christ, Mary Pat became his religious adviser and, following that with similar work on films such as Sister Act, earned the title "theologian to the stars".
"I used to get phone calls in the middle of the night asking `Was there a resurrection?'. I'd just say yes and slam down the phone - no point going into 2000 years of theological debate, just believe me - there was."
Mary Pat Kelly laughs wickedly and suddenly, all traces of the nun disappear.