Alistair McIntyre knew he had a book in him.
But first, aged 37, he had to go back to primary school in Whangarei to learn to read and write.
His teacher, Jean Smith, found him a more willing pupil second time round than she had when she first taught him 30 years earlier.
It must have been a pleasant surprise to both of them — Alistair, aka Mr Mac who operates Doug the Digger at Fieldays, never intended returning to school.
Aged seven, he had learned something that had been far more interesting when his dad taught him how to operate a digger.
"By the time I was 19 I had my own business and everything," said Alistair.
His big switch came aged 25 when he had to reconsider his future after a horrific accident in which his arm was crushed by a truck while he was at work.
That led to him starting Having Fun Co, using Doug the Digger to teach kids about diggers and excavators.
The next step was to write children's books about his adventures in a digger.
There was just one problem — Alistair wasn't too flash with reading and writing.
"I went back to school to learn my ABCs and 123s. I even had the same teacher at 37 as when I was seven.
"Jean Smith, that was her name." Alistair said.
The intervening years, and his motivation, transformed the school experience.
"There's a difference when you have to learn and when you want to learn.
"I wanted to learn now because I wanted to write these books," Alistair, now 52, said.
Two books later, Alistair still works with his diggers, but now it is on a much smaller scale teaching kids about the machinery. At Fieldays, he also had promotional copies of his second book, The Need for Listening, available.
At the Doug the Digger site at Fieldays, Ivanca Jedd, 11, loved the experience.
"It was fun. Moving the digger was much easier then I thought.
"I can't wait to go again."