Sources have been the written records of Native and Māori Land courts, the most elderly and knowledgeable of kaumātua, and the land itself. He has trekked most of the coastal region from the Waikare River in the north to Mataikona, near Castlepoint, in search of ancient pā and burial sites and tracks about which he has been told.
Councils have used him for cultural reports, and marae have used him to conduct genealogy seminars, on the back of what seems an extraordinary capacity for recall of detail, not only what, but from where.
"I get calls," he says for example, "from the Māori Land Court unable to find something. I might point them towards Māori Land Court, say minute book 38 ..."
It's required attaining a unique sense of trust from some sometimes tentative people, but resulted in the uncovering of facts and sites that in some cases not even the kaumatua or current landowners knew, a unique situation for a former school teacher who happens to have been a tennis champion, and is Pākehā and living in the Poraiti homestead in which he's lived all but about five of his 75 years.
Almost as if a warning to anyone who may follow, and there must be, he says: "I've got a good relationship with the people. But I certainly don't abuse the privilege, and that's what it is."
It takes a bit to get all of this out of Pat Parsons, but at the end of the day, there's a story to be told in terms of Hawke's Bay history, more than three decades in the making, millions of words of "focused essays," such as reports for Waitangi Tribunal claimants and documents in the Environment Court.
Parsons, who produced his first book-form history in 1997 (a history of Te Pohue and districts entitled In the Shadow of Te Waka) says recognises it needs to be much shorter, when he does get onto it.
"Yes I do," he says when asked of the literary ambition, fingering the pages of one of his sizeable notebooks, written in longhand, sometime to be committed to newer technology.
Although bypassed a bit by new technology, he has had to commit lots over the years to a computer he regards more as a "word processor," he says: "Much of it is written, but not in book form. I do these things more as focused essays."
"I have been threatening to do the Māori history and mythology of Hawke's Bay," he says.
"It's all well-established in my head. It's a case of putting it aside and focusing on it."
But, by putting it off, the knowledge grows a history and with the now-established track record, things tend to come to him as if he were the chosen receptacle of the information.
Talking of tracks, there is quite some reading, of relevance to the Te Mata Peak issue, in two reports done for the Hastings council: The 1996 Isthmus report, which he has read, and the 2013 Boffer Miskell report, which he hasn't read. Unusually, he heard of the latter for the first time only recently.
"Review of Landscape Areas and Implications for Plan Review," the latter is entitled, but both essentially state the importance of the area's landscape features, with perspectives of how and why they should be maintained.
Parsons and associates have taken issue with these things before, all the way and most notably with opposition to Cape Kidnappers golf course and resort developer Julian Robertson's intention to build a luxury lodge overlooking Black Reef, about 100m from the Black Reef gannet colony.
The proposal was withdrawn and another site found, a triumph for those wanting to safeguard the regional crown jewels.
Then there was the legal action to stop the proliferation of the Maungaharuru Range with a windfarm of turbines, possibly now of benefit for developers who may now have realised perhaps the economics wouldn't have stacked up.
The rewards were practical, but linked was the making of the point that powers to be had not understood that there were "other values" that needed to be considered. "It's something you have to educate the people with," he says.
He observes frankly that when visitors come to Hawke's Bay, they head straight to Te Mata Peak, for what they can see of Hawke's Bay.
Parsons is worried by some of the community rifts sparked by the peak debate, much of it on a whim rather than being particularly well-informed, he believes.
An iwi leadership and Craggy Range deal revealed this week, and involving a track on a new route, seemed later only to be opening a door to more concern about consultation, or limitations thereof.
"I can sense," he said, "that the longer this carries on the more the tide will turn [against support for any track]."
It's been a winding path that gets Parsons to this point, from the days at Napier Boys' High School, which he left at the end of 1960 to head for Teachers Training College at Ardmore.
Then followed a wanderlust full of teaching assignments, in New Zealand, the UK, in France, in Italy, essentially preparing people for their future.
"We've got to give more thought to what survives for the benefit of future generations," he says. "We should put steps in place for the next 100 years."
