Mike Bush has seen a lot of tragedy in his career - and he continues to face that possibility as he draws down the curtain on a 42-year policing career.

In the last 13 months, the outgoing Police Commissioner has been at the forefront of the terror attacks on the Christchurch mosques, the White Island eruption, and the current Covid-19 crisis which, if not managed well, could yet see thousands of fatalities.

But before he started the role six years ago, Bush was accustomed to tragedy. As police liaison officer for South East Asia when a tsunami swept through Phuket in 2004, he was the first New Zealand official on the scene and part of the team charged with identifying dead bodies.

"Physically seeing the 5500 people that had passed away, that was a difficult thing to work through," he told the Herald in typical understatement.

"The trauma that you experience is outweighed by the sense of achievement you get from doing the right thing."

Afterwards, a psychologist was flown up to Thailand to give him trauma counselling.

"I took him out for lunch - I paid - and he asked me if I was sleeping. I said I was and he said, 'You're okay, then.'

"I think it was a very sound diagnosis."

Bush, who steps down as Police Commissioner at midnight tonight, was made a member of the New Zealand Order of Merit for his work during the operation.

Police culture

Bush called himself a commissioner of change who improved the culture of police as well as the leadership team at the police executive.

"We've absolutely transformed the culture in terms of our values, the way we're now a really compassionate, caring police service.

"We've changed the way we lead inside the organisation, moving from what I would describe traditionally as purely a command-and-control, 'high fear, low trust' kind of leadership to a model where it's no fear and all trust."

In October the Independent Police Complaints Authority announced a major investigation into allegations of bullying and related issues within the organisation.

It said it had received "several specific complaints of bullying" which had led to a number of "more general matters" being identified that required investigation.

Police had earlier commissioned reviews into its processes for dealing with bullying, after 101 current and former employees told RNZ about a culture of bullying within police.

Officers spoken to the Herald were divided on the issue.

Some felt a bullying culture existed among certain members of the executive, from the deputy and assistant commissioners down to district commanders.

The word "toxic" was used repeatedly when staff - from seasoned officers to newer badges - spoke about senior police.

That perception was brought into sharp focus by allegations around Wally Haumaha, who was eventually appointed deputy commissioner despite criticism from the IPCA about his behaviour - though it found the behaviour fell short of the definition of workplace bullying.

Others the Herald spoke to only sang the praises of Bush and his team, saying the leadership under him was modern, dynamic, progressive and positive.

Both the IPCA and police reviews are ongoing.

Asked about bullying allegations aimed at the executive, Bush said: "The points you raise are real ones for any leadership team and we're really honest with each other, and when these things arise, we talk about them, then we address them as a team."

He said it was important to allow police to freely air their concerns about bullying.

"Bullying is a difficult subject because it's it can be quite subjective. And you've got to apply an objective test to that.

"That's why the process around it is so important, but everyone in the organisation is determined to lead in a positive way that makes people feel a sense of belonging in the organisation."

Asked if the "command and control" model can sometimes come across as bullying, he said: "That's kind of a million-dollar question."

Trust, confidence and diversity

Under Bush, public trust and confidence in the organisation on a national level has steadily increased, according to the Police Citizens' Satisfaction Survey.

In the 2018/19 year trust and confidence sat at 79 per cent, a tiny increase from 78 per cent the previous year and 77 per cent in each of the preceding years.

Bush said improved trust and confidence was one of his proudest achievements

"We've transformed the organisation, but that doesn't mean it's perfect," he said, adding that perfection in an organisation of 12,000 staff is not possible.

"But we do strive for perfection."

Increased diversity was also a badge of honour for Bush.

In 2018 the recruit wings of Wing 314 were announced as the "most ethnically diverse ever" with more than 40 per cent non-Pākehā and 54 per cent women.

When Bush took over, according to police annual reports, 70.9 per cent of the force were New Zealand European/Pākehā, and women made up just 18.5 per cent of sworn or constabulary staff.

By the end of last year, 68.1 per cent were Pākehā and the number of women had risen to 22.4 per cent.

Bush said trust and confidence in police is particularly low among Māori, Pasifika and youth, and police had worked hard to improve it.

In Counties Manukau, he said police engaged with youth and were told their approaches were often accusatory.

"We changed the interaction immediately and it had a big difference."

Police have acknowledged unconscious bias towards Māori, and it's an issue Bush takes on personally when he spends an hour addressing each new police wing.

"One of the key messages is how we, as a police service, own our role in the over-representation of Māori both as offenders and as victims in the justice system, and that we need to make better decisions to turn that over representation around.

"So on day one, I don't just give permission, but I encourage every police officer to make better decisions about how we use discretion in a way to turn that around."

Police discretion and responsibility

He said police warnings and alternation resolutions for low-level offending were not being applied evenly to Māori.

"We've worked really hard on it and it's nice to be able to report that we now apply our discretion evenly in that space."

The police apology to Tuhoe for the 2007 raids, which took place in 2014 soon after he took the top job, was one of the most "profound" moments of his career.

Bush said that was made possible by Haumaha, who Bush supported despite intense pressure to drop Haumaha from the deputy role.

Asked if the need to improve relations with Māori was a reason he supported Haumaha, Bush said: "All I'll say was it a very difficult time for Wally in his family, and it's been resolved in the reports there in black and white for everyone to read."

The responsibility on police officers to use discretion fairly has been amplified over the past year.

The recent drug law reforms mean that police are now deciding who to send to court and who to send to therapy, while the current national state of emergency provides police with extraordinary powers to stop anyone from doing anything or being anywhere that could contribute to the Covid-19 outbreak.

"How we apply our discretion is critical to building trust and confidence," Bush said.

"The one thing people look for is the consistent application. And that's what we've been driving hard."

As the very public face of police, Bush himself has had a hand in shoring up public opinion, particularly during the terror attacks in Christchurch last year.

Watching footage of the gunman's video was the most horrific thing he'd ever seen in 42 years in police.

"And to watch it almost in real-time had an impact on everyone in that room," Bush has previously told the Herald.

Distinguished career - with black spots

Bush joined the police in 1978 as a young constable, and five years later found himself pleading guilty to a drink drive charge.

He had been drinking with a colleague over dinner and was dropping the colleague home, after wrongly believing he was "right on the limit".

"I was very disappointed in myself," he said in 2017, when he front media about the conviction six months after he had been reappointed Police Commissioner for a second three-year term.

He was fined $250 and disqualified from driving for six months.

He nevertheless rose through the ranks, holding leadership roles in rural, provincial and urban areas before becoming district commander in Counties Manukau by the mid-2000s.

He pioneered neighbourhood policing, which has since been rolled out across the country.

Bush was also instrumental in the capture of infamous drug lord Brian James Curtis, who was living in the Philippines under a fake identity.

Curtis was caught out by technology when his fingerprints - taken after he tried to cash a forged cheque - matched those supplied by Bush to Interpol databases.

As deputy commissioner he was in charge of policing the 2011 Rugby World Cup, and also led the rollout of smartphones and tablets for frontline staff.

He was criticised for praising disgraced police officer Bruce Hutton at the Crewe murders investigator's funeral, which Bush later apologised for; Hutton had planted evidence that led to the wrongful conviction of Arthur Allan Thomas.

Those comments about Hutton blighted Bush's appointment as Commissioner in 2014. At the time, the Opposition Labour Party's police spokeswoman said she hoped Bush would have acted differently with hindsight.

That spokeswoman was Jacinda Ardern, who would become Bush's boss and work closely with him through the response to the March 15 terror attack.

What's next?

That relationship with Ardern will continue for some time as Bush works through the current threat of Covid-19 as part of the national response team.

Bush was meant to finish up as commissioner and then head to Italy with his wife, but that has been put on hold as the global Covid-19 pandemic marches on.

"It will be a while before my wife and I travel to Italy, but it will happen."

The Police Commissioner reins will be taken up by Andy Coster, but Bush will remain on the national response team for "as long as it takes".

If Bush has any regrets about his tenure as commissioner, he didn't reveal them, saying there were no low points whatsoever, nor were there any policies or programmes that he failed to get over the line.

Nor would he give any position on the trial of police armoured vehicles or the use of the Eagle helicopter in Christchurch, saying only that those pilot programmes would be properly assessed.

He said his high point was the commitment and professionalism of police who put themselves in harm's way to protect communities.

"They make massive decisions every day and every night which impact on other people's lives. And 99.9 per cent of the time they get it right.

"It's been an absolute privilege not just in the last six years but the last 42 years to be a part of - but I'm biased."