Described as a trusted lieutenant and a "safe pair of hands", Mockridge was the chief executive of Sky Italia (also owned by Murdoch) and has spent the last 18 months at the helm of a company seen as the poster child for all that is wrong with the media.
It's been a tumultuous time. More than 20 Sun journalists have been arrested as part of ongoing police inquiries, including Brooks.
Mockridge himself was questioned at the Leveson Inquiry, giving evidence on behalf of News International about a time when he wasn't in the country, let alone in charge.
He could not defend what had taken place in some of his newspapers, but was a staunch advocate of a free press in Britain.
By and large, Mockridge was seen to have made the best of a bad lot and suggested as a frontrunner for a top job under Murdoch's new business structure.
But he was overlooked as the chief executive of the newly formed publishing division of News Corp - which has been split from the more profitable entertainment - and resigned on Sunday night.
There was a public exchange of platitudes, with Murdoch describing him as a "skilled executive and "trusted friend", and Mockridge saying his mentor had "the vision, the guts to make risky investments but also the willingness to put great confidence in me (and others like me) to get on with it".
But his disappointment was also obvious.
"To be direct, the reason I am leaving is that the new structure does not offer me a role I am comfortable with, and after 22 years with the company in five countries, I feel I have made enough of a contribution to make a personal choice to go," he wrote in an internal message to News International staff.
Mockridge leaves at the end of the year and will be replaced by another New Zealander, Mike Darcey, currently the chief operating officer at BSkyB in Britain.
Darcey declined to be interviewed until he officially takes over in 2013. But in his first interview since making his announcement, Mockridge met the Weekend Herald at News International HQ, in east London.
Wapping is a long way from the Taranaki Daily News, where he started his career as a cadet reporter based in the Taumarunui branch office.
"I've had a little bit of luck. And you make your own luck."
He bought a one-way ticket to Australia in 1980 and ended up as a financial journalist for the Sydney Morning Herald.
The 1980s was a time when financial stories were "newsy", more likely to be on the front page than the business section.
Moving among the movers and shakers in the capital, Canberra, it wasn't long before Mockridge moved into politics as an adviser to Australian Treasurer Paul Keating, who went on to become the Prime Minister.
Mockridge spent seven years with Keating, a time he describes as the most stimulating period of his career.
"It was sensational experience. He was a charismatic, forceful man, a do-er. It was a chance to work with the elite of public service in Treasury and I was exposed to some of the best brains in the country."
Then Murdoch came calling. His right-hand man at the time, Ken Cowley, recruited Mockridge into the News Ltd empire in 1991 and he quickly climbed the ranks to become chief executive of Foxtel, the company's pay-TV division, then Star TV in Hong Kong.
That was followed by an 18-month stint back in New Zealand, a return to his roots after two decades away.
He was appointed managing director of Independent Newspapers Ltd, a subsidiary that controlled News Corp's papers in New Zealand such as the Sunday Star Times and the Dominion Post, as well as being chairman of Sky TV.
Murdoch called again.
"I was at a charity auction in Auckland and I got a phone call around midnight from Rupert. He said 'can you come over to Milan, there's something I want to talk to you about'. I hopped on a plane."
The plan was to oversee the merger of two pay-TV networks, Stream TV and Telepui, into Sky Italia and become its first CEO.
For most of the past decade, Sky Italia battled for ratings and revenue with Mediaset, owned by Silvio Berlusconi - who also happened to be the Prime Minister at the time.
Mediaset owned most of Italy's free-to-air television network but launched a satellite channel to compete with Sky. Berlusconi's government then changed the laws to disrupt Sky's programming, double the taxes it paid and restrict advertising.
Mockridge has never complained about the uneven playing field.
"Italy is a challenging business environment. One of the strengths of the country is a strong sense of tradition, family, community. If you look at it from the other side, that can be seen as insular and reluctant to change," says Mockridge.
"A foreign company can find that challenging. If we hadn't had a brand name as strong as Rupert Murdoch, I think it would have been virtually impossible to build the company as we did. He was such a respected international figure, the press used to refer to him as 'the shark' ... in a positive way. That gave the business community the certainty that we would stay for the long haul."
By this time, Mockridge was happily settled in Milan for eight years with an Italian wife, Lucia, and their two children, Filippa and Rodolfo.
While Sky Italia was going from strength to strength, News International lurched from one crisis to the next. He got another phone call from the boss.
"It was 'come up to London'. I was in Germany at the time and I flew up that afternoon, came in here [News International headquarters] the next day," says Mockridge.
"I didn't go back to my office in Milan for three months. I came in here and it was head down and bum up."
After years of stories about celebrities which were gleaned from voice messages on hacked phones, the tipping point was the search for missing schoolgirl Milly Dowler.
Revelations that News of the World reporters had hacked into her phone and accidentally deleted voice messages - giving false hope to her parents - was the catalyst for change.
An outraged public demanded action. News of the World, the most popular paper in Britain, was shut down and dozens of journalists arrested, including senior News International executives such as Brooks.
One of the first things Mockridge implemented was the Management and Standards Committee, which sifted through hundreds of millions of emails to look for evidence of journalists paying bribes to police for scoops, or other cases of phone hacking.
Anything dubious found was handed over to the police for further investigation, leading to more arrests of Sun reporters this year.
Simultaneously, Lord Justice Leveson held a 16-month inquiry into press practices, which heard from hundreds of witnesses, including celebrities such as Hugh Grant and victims of intrusion such as the Dowler family.
Mockridge also gave evidence at the hearing, just six months after taking over from Brooks in July 2011.
After answering questions about editorial policy changes since his arrival, Mockridge was asked by Lord Justice Leveson to share his thoughts on the British press as a "newcomer" with significant journalism experience overseas.
What followed was a robust defence of an independent press free from Government regulation.
"But there is a difference, isn't there, between state intervention and state provision of a mechanism which permits independent regulation?" asked the Lord Justice.
"I don't accept that," replied Mockridge. "Once the state intervenes, it intervenes."
He went on to say that journalists around the world are jealous of the British press, which has strong readership and resources to examine issues and hold people to account.
"So everything might not be perfect but if we look at the great array of stories published in this country over the past decade, there is only a minute fraction of them which have been of particular interest to this inquiry."
This earned a mild rebuke from Lord Justice Leveson, to which Mockridge clarified that he did not condone any unethical behaviour committed by journalists.
"But I think in general this country enjoys something precious, and something I must say many people in other countries look up to. I think that's a balancing thing that needs to be very seriously considered."
Just days before the Leveson Report was made public, Mockridge was on a BBC radio show, saying that state-regulated press would be "crossing the Rubicon" - a phrase echoed by Prime Minister David Cameron in choosing to ignore the main recommendation of the inquiry.
Mockridge told the Weekend Herald that newspaper editors had to come up with a system of regulation to "be held accountable and show the community that we're serious.
"But it doesn't mean we want the Government to do it. It's a fundamental thing that since 1694 the Government stays out of what the press does. That's something we've inherited in New Zealand. Maybe we take it for granted.
"There were things that went very wrong in the News of the World. Since then we've had people get arrested and charged, including at the Sun. We had to take our medicine.
"But our argument is that there are laws to take care of that. You don't have to change the constitution of your country."
Yet just a few days after the Leveson Report was published, Mockridge is gone.
He was seen as the frontrunner for the new job as the head of News Corp's publishing arm but was overlooked in favour of Robert Thomson, the current boss of Dow Jones and The Wall Street Journal.
Media commentators are surprised at Mockridge's exit and Murdoch insisted his "decision to step down is absolutely and entirely his own. I am sorry to see him leave us but I know he will be a great success wherever he goes."
As for Mockridge himself, he is coy about the future.
"We'll see what the New Year brings. I'll be busy until then."
