Key Points:

Tuhoe Isaac knows the walls of prisons well.

Twenty, 30 years ago, he did some evil things, and was imprisoned inside them, he says.

In November the former Mongrel Mob president issued his biography, True Red, his story about becoming one of the country's most infamous mobsters.

It tells how he got in to the mob, the crisis that drove him out and how his belief in God has kept him free of that life for 17 years.

In his heyday the 53-year-old, whose mob name was Bruno, commanded every vice. Women, money, drugs and crime.

His charisma led to then-Prime Minister David Lange attending a mob convention - a gathering that ended in the abduction and pack rape of an 18-year-old girl in 1986 and put the words Ambury Park - the South Auckland site of the rape - into New Zealand's consciousness.

As the chairman of four mob chapters, Isaac could impose retribution on other gangs, including ordering death if circumstances warranted it.

Although he is not a tall man, his shoulders are wide and he could beat someone senseless.

Such was his power that to run a smooth prison that guards gave him free rein to control his people.

That's a life left far behind, he says.

The physical resemblance to the man he was remains evident - his mob tattoos are etched for life. But today, he's a jovial character. He's got a mean little Maori giggle, and gives off a happy-with-life born-again Christian vibe.

Prison visits, however, remain a big part of his life.

Once a week, Isaac travels from his Pukekohe home to visit youth offenders at Mt Eden Prison for an hour and a half.

He has just finished reading some of his story to youth offenders and is sitting outside the remand centre, all black T-shirt and leathers. There's comfort in a black shirt, he reckons.

He plans to read a chapter of his book to the boys on each visit.

"We're only up to chapter two," he laughs.

They ask him questions, talk about abuse, life in the gangs, and they try their luck and ask how he made alcohol when he was in prison.

Although he wants to help those heading down a path he trailblazed, he's under no illusions that his book will save the world.

"They can do whatever they want to do. One guy says 'what do I have to do to join the Notorious [mob chapter], bro?'

"I said to him, there's one thing I want to share with you - just expect the consequences. There's no judgment from me."

I first meet him shortly after the terror raids on his iwi, for which he is named.

He was unimpressed with talk from some suspects about hits on political figures such as John Key.

"We didn't just talk about doing things. We just did it. If we set out to kill someone we did."

It's a frank assessment of his gang life.

But then he's an open sort of bloke.

Ask him about past crimes, he'll talk about them; drugs, he'll talk about them; violence ... nothing is out of bounds.

The book doesn't try to excuse any of his behaviour, it just lays it all out and explains why those entrenched in the colour red and "mongrelism" did the things they did.

It's not so much the storytelling that draws people in. You keep reading because for many Kiwis this is the closest they will come to understanding the inner workings of a gang.

Some bits do grate, none more so than his claim that a theme runs through his life of being wrongly blamed at different times for predatory acts against women, and then likening his experience to biblical characters also wrongly fingered.

It's put to him, it was hard not to feel angry he felt aggrieved about being wrongly locked up for a rape in 1983 - of which he was found not guilty at appeal - because it wasn't as if he hadn't participated in gang rapes before.

"You have a right to feel that way," he replies .

"Before, women were just sex objects to me. They were there for my pleasure. That's how it was."

People ended up in gangs in the 1970s and 80s mostly because they were rudderless, fatherless, lost figures - being in the mob was about hate and anger fuelled by poverty, little education, loneliness and societal rejection, he says.

He was sexually abused as a child by family associates, and left home in his early teens for a trades apprenticeship. Alone in the city and without any real boundaries he didn't finish the course, went to Australia, ended up in prison and fell in with gang members on his return to New Zealand.

He was nasty, but there was little choice, he says.

"I became that because I had to learn survival within that structure. I had to learn how to keep that mongrel mask on. Not showing any weakness, I carried all that through my gang life.

"I was angry. It did not connect to me, I was an angry person, I would just fight. People just gravitated towards a form of comradeship - because they're lacking it. It's in our culture to belong to our tribes, our iwi, our hapu."

But identifying as Maori wasn't something many did when he was in charge. Going to marae was intensely uncomfortable, and as far as members were concerned they weren't Maori, they were mobsters.

The impetus to change came from many factors - the fallout from Ambury Park, thinking he had HIV, getting sick of crime, taking the rap for the 1983 rape, and the beginnings of a spiritual awakening.

But breaking bad habits needed something extreme, he said.

Exploring his Maoritanga wasn't enough to steer him away from gang life, but it does explain the full facial moko.

If you want extreme, God fits the bill, and is the only option that works for hardcore criminals, he says.

"There's nothing else that can change us. Unless you've got a personal relationship with God there's no way of knowing you've changed, you might think you've gone through change. It's too hard to do it alone." Author Bradford Haami said he wanted to find out more about the psyche of members and the difficulty in changing a mindset.

"I didn't want to write anything that glorified his ganglife, I wanted to know why he did the things he did, the mentality of someone caught up in that world," he said.

It took a lot of guts to change your life and Isaac had that in spades.

"He says in the book he feels people's judgment like maggots crawling all over his skin. But he's going to live with the consequences of his past for the rest of his life."

People's judgment doesn't seem to be worrying Isaac on a quiet midweek day in Pukekohe. He's on the main street camped outside a retail shop selling his book.

He's a good salesman. Old ladies with blue rinses stop for chats and leave with hugs.

Selling dope was much easier, he jokes, but life now is more fulfilling.

He has four children aged between 5 and 20, is a motivational speaker, is asked to attend primary school prizegivings and runs men's programmes.