He was promoted to detective and then spent time as a tactical firearms officer, covert surveillance operative and National Crime Squad trainer.
After several trips to New Zealand and loving the place, he joined the New Zealand police in 2003.
Three years later, he set up a training and consultancy business, and now lives in Auckland with his partner Sallie, an artist.
"It is thanks to Sallie I was able to write my book," Austin says. "She gave me 'permission' to leave work and follow my dreams.
"I know it's not the best book in the world," Austin says frankly. "However, one of my strengths is knowing my weakness. And as Sallie said to me, I've done my bit now. The rest is out of my hands. She also told me not to get too precious about any criticism. Sound advice I think.
"I wrote this book to see if I could do it. I've enjoyed the whole process.
"It's been a bit like being on a rollercoaster. You just never know what's going to pop up in your email or who will be on the phone."
He has already written his next book. Agency is the first of a trilogy in which Austin draws on his investigative skills.
"Sallie asked me recently what was the first thing I thought of in the morning and the last thing at night," Austin says.
"At first I thought, 'oh-oh, this is one of those trick questions'. So of course I said 'you dear'. Sallie laughed.
"She is an artist and she said the first and last thing she thinks of every day is her art. And yes she's right. The first and last thing I think of is writing.
"So now I'm going to be brave and call myself a writer."
And so he should.
Twitter @LindaHallnz
