The Solicitor-General is officially the junior legal officer to the Crown's senior legal adviser, Attorney-General Chris Finlayson, who approved the appointment.
In reality, he is the Government's chief legal adviser and advocate, the chief executive of the Crown Law Office and responsible for the prosecution of serious crime nationwide, through Crown Solicitors.
Mr Finlayson said the Solicitor-General's job was one of the hardest in government.
"Not only does he or she have to be chief executive of what is in effect a little Government department, that person also has to be nation's top litigator and also the top non-political legal adviser to Government."
Hypothetically he could be in the Supreme Court on a very difficult matter, come back to the office to prepare submissions for the next day, be urgently called over to Parliament to give an urgent opinion to a minister and have to oversee the running of an office of 188 fulltime-equivalent staff.
Mr Heron has practised in London, Tokyo and Auckland. Sports law is part of his breadth of experience as well as criminal, civil, commercial, human rights, health and public law.
In 2007, he co-authored a review of the All Blacks' failed Rugby World Cup campaign for the New Zealand Rugby Union.
Mr Heron is now in London for the Olympics, where he will be going to some rowing, athletics, cycling and beach volleyball and seeing out some of his last duties as chairman of Drug Free Sport New Zealand.
Trevor Mallard, when he was Sports Minister, appointed him to the job and still holds him in the highest regard. "He is an absolutely wonderful guy," Mr Mallard said this week.
Auckland Crown Solicitor Simon Moore, who worked with Mr Heron for 12 years at Meredith Connell in Auckland until 2007, was equally complimentary. "This is a magnificent and inspired appointment."
And every person he had spoken to within legal circles, including judges, thought so too.
"Everyone, everywhere you go, people are saying this is a terrific appointment."
Mr Heron moved across the road in Shortland St to Russell McVeagh to increase his commercial and civil experience and recently left a partnership there for the independent bar.
He has been one of the special advisers known as panel counsel to the Serious Fraud Office, the Auckland Crown Solicitor and the New Zealand Law Society.
His last high-profile client was the late Allan Hubbard, the South Canterbury Finance founder who was killed in a car crash while facing charges laid by the Serious Fraud Office.
Simon Moore said Mr Heron had an aversion to pomposity.
"As a criminal advocate in Crown prosecution work, he had a rare ability to engage with juries. Juries liked him, they trusted him and he did very well in that work."
Mr Moore added that being a genuinely humble person, Mr Heron would curl up in a ball if he heard the praise being heaped upon him. He said the Solicitor-General was not political but needed to be aware of political realities.
"It also requires, as with many lawyers, a real understanding of what is the right answer which meets the best interests of the client.
"It's not just a question of being a superb black-letter lawyer but also being someone who is practical and has that practical hands-on experience to know what is the best answer or solution for their client."
Mr Heron grew up with the law. His late father, Justice Richard (Dick) Heron, was a legendary figure in the High Court at Wellington, well liked and respected.
Heron junior went to Wellington College, where he was head boy in 1984.
Mr Heron, aged 45, will replace David Collins, QC, who has been appointed a High Court judge - and who coached Mr Heron in the Victoria University rugby team.
The team went on to be coached by former All Black captain Jock Hobbs, who died in March.
Two of Dr Collins' deputies, former law professor Matthew Palmer and Cheryl Gywn, are thought to have been the other two short-listed. Dr Palmer has since announced his resignation to colleagues.
The Crown Law Office has been subject to several reviews in recent years, a particularly critical one under the Performance Improvement Framework run by the State Services Commission, the Treasury and the Department of the Prime Minister and Cabinet.
Mr Heron's brief, like many other agencies of the Crown, will be to improve its performance under fiscal constraints. He will be required to keep a tighter rein on the costs of public prosecution, which blew out under Dr Collins, and to provide a more cohesive structure for legal advisers across the whole of Government.
Mr Finlayson defends Crown Law's record, citing recent wins, including tax cases against banks that boosted revenue by several billion.
But Labour shadow Attorney-General Charles Chauvel believes there are issues there about performance.
He cited the Urewera raids, the Dotcom case and the Teapot Tapes saga, in which the Solicitor-General intervened in a civil matter during an application in an election campaign to stay any prosecution against the cameraman who taped a conversation of Prime Minister John Key.
"A lot of legal commentators would say Crown Law hasn't been performing on a stellar basis. And it's not that they lost the cases, necessarily. It's just that for such high-profile ones, their involvement didn't seem to be well resourced and well thought through."
Mr Chauvel knows Mr Heron, having graduated from Victoria law school with him in 1989.
"What I would hope Mike will do is provide a highly professional leadership to that office that shows an understanding that their job is to defend to the utmost the Crown's right to act within the law but to be very clear to the Crown what the limits of that is in terms of what is politically appropriate."
Mr Moore said the difference between the ordinary lawyer and the really good lawyer was the possession of an instinct in relation to legal principle.
"What I think is one of the most important qualities in the Solicitor-General is a rigid adherence to the principle of independence. They must be able to provide the Government with the best legal-practical advice but at the same time ensure ... that advice is objective and impartial.
"I am absolutely certain that he has those qualities and he has those qualities in abundance."
