Dr John Wood describes it as a "hallelujah moment". After years of discussion, Tūhoe accepted the groundbreaking idea of giving their beloved ancestral homeland, Te Urewera, a legal personality as part of their Treaty settlement deal.
They wouldn't own the National Park - instead it would be a unique legal entity, with all the rights of a person - jointly managed by Crown and iwi.
It was a world-first arrangement later replicated in the Whanganui River Treaty settlement, which Wood was also involved with.
Wood, a career diplomat who'd spent two terms as ambassador to Washington, had no legal background or in-depth knowledge of Māori grievances.
But during lengthy negotiations he became fascinated by the work of early 20th Century lawyer Sir John Salmond, who wrote about "legal fictions".
"This had been thought about for more than 100 years but no-one had actually done it - giving personality under law to a large natural object."
A stumbling block in Tūhoe negotiations was the fate of Te Urewera. Without it being included in the settlement there would be no deal - but then-Prime Minister John Key had ruled out transferring ownership to Tūhoe.
The parties had to think outside the square.
"Tūhoe began by thinking they needed ownership of the National Park in a European legal sense because that was how the conversations had been framed over the past 100 and something years," Wood says.
"It turned out that wasn't what they wanted at all and in fact wasn't consistent with their own world view - if you believe that a large natural object ... is a living ancestor then how could you contemplate owning it?"
Wood had retired from the Foreign Ministry when he was approached by then-Treaty Negotiations Minister Chris Finlayson to work as a Crown negotiator, on the recommendation of Wood's old colleague and then-Trade Minister Tim Groser.
"I'd been the country's top trade negotiator and advisor for years. [Groser] basically said 'if you're looking for a negotiator, then go and get hold of him'."
Why did he accept?
"For the same reasons most people of my generation whose careers are effectively over would feel - how many more generations are going to go by before these settlements are reached and the grievances dealt with?"
The job has been financially rewarding - figures released under the Official Information Act show Wood has been paid almost $1m for his work, which he does on top of his role as chancellor of Canterbury University.
What does he say to critics who call it a gravy train?
"I think people have got to make up their own minds about those things - it's all public and open and transparent, it is what it is."
Wood was shocked by what he saw when he first visited Te Urewera a decade ago.
"The only provision ... of Crown medical services was a monthly visit by a GP for one day ... by prior appointment only.
"You've only got to go up into those areas to see the level of deprivation, rural housing with rheumatic fever written all over the doors ... a general sense of, 'if we don't fix this in our generation, more generations are going to go to waste', basically."
Population-based formulas were never going to provide comprehensive government services for the people, he says.
"It was quite clear the tribe was going to have to step in and look after its own people to a much greater extent."
The key to reaching a settlement was taking the time to understand the tribe's needs and aspirations.
"It's a conversation that can be a very long one, the Tūhoe one we're talking about several years. The outcome of the process is often a surprise to both parties."
Despite what people might think, money is seldom the central focus for iwi in Treaty negotiations, Wood says.
"There isn't an obsessive focus on financial issues and money. Do compromises have to be made? Yes they do, and some of those are very hard.
"Being brutally frank this is not about compensation, of course the country could not afford to compensate in monetary terms for everything that's happened in the past, so it's ... to try and provide a better economic basis for the iwi to move forward."
Negotiations can be emotional.
"There's a lot of anger against the Crown, justifiably.
"In addition to anger there's a lot of regret and that's mostly around the fact that past leaders who began the process ... are no longer here."
Wood says there is no particular training for Crown negotiators - they are given a handbook known as the "red book" to help prepare.
"I've never actually managed to get my way entirely through it.
"We're effectively responsible for the strategy, backed up by professional teams of young, passionate, committed people from the Office of Treaty Settlements."
Wood is also involved in Taranaki and Central Plateau negotiations, which takes him away from home a lot.
He says the country should be proud of what's been achieved so far.
"We've all got to get out of grievance mode. If we've done our job, we've resolved these historical grievances but we've also provided the platform and relationships that will take everyone forward.
"The end point will be when all those who are willing and able to settle, have settled, and I think we can get there."