An expert Norwegian team involved in terrorist and murderer Anders Behring Breivik's imprisonment visited New Zealand months ago to advise Corrections on how to manage the alleged Christchurch terrorist.
The visit makes the failure in vetting the alleged offender's mail doubly disappointing, Corrections Minister Kelvin Davis told the Herald.
"It is sensible that people who have experience in looking after this sort of prisoner were here to help and guide us.
"That's why I'm particularly disappointed that this situation has occurred with regard to his mail, and why we've taken steps to make sure it never reoccurs."
Davis has demanded a new process following the failure of Corrections to keep one of the accused's letter, using language about a call to arms, from being sent to a person in Russia.
All mail to and from the prisoner will now have to be signed off by a team of senior prison staff, intelligence staff, Corrections psychologists, partner agencies and the chief custodial officer.
Corrections chief executive Christine Stevenson will then have the final say.
The former process was to have letters reviewed by intelligence staff, and then signed off by the prison director.
"That process let us down," Davis said.
"There weren't enough layers of scrutiny for this prisoner. I've instructed Corrections to implement a more robust process with more layers of scrutiny, to be signed off at the highest level."
Following a meeting this afternoon with Corrections chief executive Christine Stevenson, she was immediately putting in place changes to the system by centralising the review of these prisoners' mail into a single specialist team.
"The letter is further proof we need to ensure our current laws are fit for purpose. I will discuss the issue with Cabinet on Monday."
The alleged offender has tried to send nine letters; seven were sent and two were withheld.
Of the 48 letters that have been sent to him, 14 were withheld, 16 were being scrutinised, and the remaining 18 were given to him.
Corrections had double-checked the 18 letters to make sure none of them should have been withheld, Davis said.
"There are no issues or concerns with any of them."
And it has emerged tonight that a second letter had been sent by a serving inmate that should have been withheld.
The second letter was sent from a prisoner "holding extremist views" at Christchurch Men's Prison - believed to be Philip Neville Arps, who was jailed this year for distributing an objectionable publication after the March 15 shootings.
"This is totally unacceptable, it should not have happened, and I apologise for any further distress this has caused," Stevenson said.
Davis did not meet with the team from Norway and did not know details of their advice to Corrections.
Breivik, who killed 77 people in 2011, is a keen letter writer but his letters are vetted to prevent further crimes or hate attacks.
According to Norwegian news outlets, Breivik told a court in 2016 that only about five out of 300 of his letters had been delivered, and by 2016 about 600 out of 4000 items posted to or from Breivik had been confiscated.
Norwegian freelance journalist Asne Seierstad told the Herald in late March that denying Breivik the freedom to write to his followers only happened after he was convicted.
"He's a very devout letter writer. For the first few months [prior to trial] there were no rules. So in the first few months he sent and received letters, even to followers and supporters and fans. But that was stopped in August after the verdict.
"It's not the fact he can't write political content. But he can't communicate with people who they fear to be followers, or people who have been convicted for whatever reason earlier. And these are the people he wants to be in contact with. And that's what he lost."
Davis said the failure over the letter was a chance to review all aspects of the accused's strict incarceration rules at Auckland Prison.
"His confinement is very closely monitored and managed. He doesn't have contact with anyone other than his own lawyers or the prison officers who are watching over him 24/7. He has no association with any other prisoners, for their safety and for his.
"Staff are hand-picked and have a lot of training in terms of how to manage him. There aren't pathways for him to send mail out via other channels.
"There is absolutely no way he has anything like [a mobile phone]. He has just the very basic necessities in his cell."
Davis said the law would also be looked at, adding that inciting hatred could be a further reason to withhold a prisoner's letters.
He said it was "quite likely" that the prisoner's letter should have been blocked under the Corrections Act on the grounds that it could endanger someone, or encourage an offence.
Other reasons to withhold mail under the Act include threatening or intimidating a person, posing a threat to the security of the prison, and prejudicing the maintenance of the law.
Davis said he still had confidence in Christine Stevenson, who has apologised for the error, and was not going to call for heads to roll.
"It's just unfortunate this situation has occurred, and she has apologised unreservedly for it, and I think that's sign of what a great chief executive she is."