National MP Sam Uffindell believed his assault on a younger boy while at Auckland's King's College 23 years ago would become public during his running in the Tauranga byelection this year.
When it didn't, Uffindell chose not to tell the public until it was revealed today - a decision he still stands by, despite saying he had "taken ownership" of the incident and it had made him grow as a person.
He also revealed he may have tackled other students during the "raid" of the third form (Year 9) dorm that saw him pushed out of the school, in addition to punching one student in the arm and body several times.
It was revealed by Stuff today Uffindell - who won the Tauranga byelection in June - had apologised to the boy he assaulted in 1999 while at the Auckland boarding school.
In multiple interviews, he claimed it was the "stupidest" thing he'd ever done and still regretted the incident.
While the victim claimed he was hit with unscrewed wooden bed legs, Uffindell couldn't recall whether he used them during the beating.
A statement from the National Party said the party had been "proactively informed" about the incident by Uffindell during the selection process ahead of the Tauranga byelection.
"It was a significant event reflecting a serious error of judgment by a then 16-year-old for which he has apologised and regrets to this day," the statement read.
Uffindell wasn't sure whether leader Christopher Luxon was informed of the incident when the party was informed and he hadn't spoken to the party leader today.
The incident reportedly occurred on the last night of term inside one of the King's College boarding houses.
Uffindell, along with three peers, ran into the dorm, possibly tackled students before punching one student several times on his way out of the dorm.
He wasn't aware of what happened afterwards.
Uffindell rejected the suggestion it was hazing and would not comment on the culture at the school.
The day after the incident, Uffindell said he was called to a meeting with the school headmaster John Taylor, his house master and his parents.
Uffindell said he was then asked to leave the school but he acknowledged it was a polite way of the school telling him he must leave.
He completed his schooling at St Paul's Collegiate School in Hamilton.
Fast forward two decades and upon his return to New Zealand from working in banking overseas, Uffindell said it had "struck him" that he needed to apologise.
He then contacted a family member of the victim so he could make a "full apology" to the victim.
According to Stuff, the victim eventually forgave Uffindell until he learned of his political ambitions.
"... a few months later I sat down to watch the news on the couch with a beer and there he was, running for Parliament," the victim said. "I felt sick."
Uffindell estimated he apologised just after Easter last year and did not feel it was necessary to mention his aspirations in politics.
"I just rang him up to apologise, I wasn't trying to call him up for political purposes ... I wanted to atone for what I had done."
During the selection process within the National Party ahead of the byelection, Uffindell submitted a written account of the incident to the nine members on the selection committee, whom he wasn't sure whether he could name while speaking with the Herald.
Confident he had given an accurate account, Uffindell said the party members recognised it was a serious incident but they reportedly appreciated Uffindell had been upfront and that he had apologised.
Uffindell said he suspected it would be revealed while campaigning in the byelection but kept quiet when it didn't.
"We expected it to come out in the byelection at some stage and it didn't, but it's come out now and it is a highly regrettable and significant incident and I take full accountability for it."
He claimed National Party members were not part of the decision not to speak of the incident publicly.
Asked whether it would have been responsible to release it given the development it had caused in him, Uffindell said: "We're doing it now, I don't have a response to you on that".
In a Bay of Plenty Times question and answer article in June in which candidates were asked, among other questions, what were their biggest mistakes, Uffindell replied: "Not coming home to New Zealand sooner. There's nowhere we'd rather raise our kids".
Asked whether he would change this, Uffindell said a question and answer forum wasn't an appropriate platform to discuss such an incident.
Act byelection candidate Cameron Luxton, who revealed his drink-driving as a teenager while answering that question, believed Uffindell wasn't being honest to voters.
"I was upfront at the time ... I was drink-driving as a teenager and it's been my biggest regret and it's something I thought that you should be honest about.
"I disclosed it to Act and they agreed that voters deserved to know before they cast their vote."
King's College headmaster Simon Lamb said in a statement: "The issue referred to in the Stuff article today was a matter which the College dealt with 22 years ago. Since that time, the College has not been involved in any follow-up activity with those involved, including the recent discussions reported in the article."
Lamb said the school does not wish to comment further on the article.
"We have confidence in our disciplinary and pastoral care processes and we are clear in our messaging to the whole community that it is every student's right to feel safe at school," he said.
At a post-Cabinet press conference this afternoon, Prime Minister Jacinda Arden said the conduct of candidates and MPs was an issue for the party involved.
Asked about any hypocrisy given Uffindell has been campaigning for stronger action on gang violence, Ardern said as leaders "we need to be accountable for our members' conduct".
"It is up to the National Party and [leader] Christopher Luxon how they conduct their own affairs."
Deputy Prime Minister Grant Robertson said violence and attacks on young people are something all people should be very concerned about.
In 2014, allegations of hazing, which involves rituals or other activities intended to harass, abuse or humiliate subordinates or newcomers, at King's also emerged.