Lessons are hard ones, despite Kate Wilkinson's soft exit.
The two-volume, 440-page report of the inquiry into the Pike River mine disaster is an exemplary piece of work - thorough, comprehensive, rigorous and surely one of the most hard-hitting produced by a royal commission.
The report cuts a lot deeper, however, than simply fulfilling the commission's prime task of apportioning responsibility for the loss of 29 lives.
The ramifications of the inquiry's findings are potentially huge.
They stretch way beyond a drastic and belated tightening up of health and safety regimes and inspections of underground coal mines.
Because large chunks of the report deal with the adequacy of regulations, the commission's conclusions have relevancy not just for health and safety practices in other accident-prone industries, but beyond.
There cannot be a single chief executive of any government department who has not pondered this week whether the regulatory regimes underpinning his or her department's operations are working effectively, be it gambling licences, telecommunications policy or whatever.
In highlighting the decline of the Department of Labour's coal mining inspectorate in terms of staffing and expertise to the point where it could no longer do its job, the report places big question marks over the wisdom of the deregulatory thrust of the 1990s which placed much more onus and obligations on employers to comply with health and safety standards.
It is here that the report may have major influence on political behaviour and bureaucratic practice. It confronts the kind of blinkered ideological mindset which decrees there is one way - and one way only - of doing things.
What the royal commission has essentially stated is that such a "one size fits all approach" should not have been applied to the hazardous conditions of underground mining.
That National was wedded to deregulation and Labour did little in terms of reversing it should have prompted MPs from both parties to have kept their heads down this week.
Not so in Labour's case, however. Its frustration was that Labour Minister Kate Wilkinson did not follow the usual script of a minister in trouble.
Instead of dragging out the agony - as was the case with Nick Smith's departure from the Cabinet earlier this year - Wilkinson announced she was "doing the honourable thing" and resigning just as the embargo was being lifted on publication of the contents of the royal commission's report.
The net result was that Opposition parties could not spend the rest of the week demanding heads had to roll when one had toppled already.
The sense of anti-climax was further accentuated by David Shearer saying Labour would accept its share of responsibility.
This might have been the sensible tack for Labour to take. But the Labour leader's gesture was obviously too namby-pamby for the likes of Trevor Mallard and Damien O'Connor who spent the rest of the week conducting an unseemly show trial of Wilkinson in her absence.
There are occasions when the politics is best left at the door of the parliamentary chamber. This was one of those times.
But Mallard and O'Connor had points to prove. As Minister of Labour in the latter stages of the last Labour Government, Mallard might have been excused for raising his eyebrows at Shearer's stance.
Mallard, who hates to waste an opportunity to give his opponents a good rucking, wanted it known that as minister he had initiated a review of mine safety following two mining-related deaths in 2006. Wilkinson inherited that review with the change of government in 2008 and did nothing of note in response.
However, this raking over the coals - so to speak - only highlighted the fact that Labour was also complicit in the rundown of the mining inspectorate during its term of office.
Mallard might have remedied that had Labour won in 2008. But Labour lost that election.
The crux of the commission's report is that an effective regulator would have acted more decisively at Pike River and probably would have issued a prohibition notice stopping the methane-accumulating hydro mining which the company began two months before the disaster.
O'Connor, the West Coast-Tasman MP, persisted in targeting Wilkinson by demanding National explain why she was still a Cabinet minister.
Deputy Prime Minister Bill English pointed out that Wilkinson had taken responsibility for the failings of her department.
That was more than could be said of O'Connor who, as Corrections Minister in the last Labour Government, had refused to resign after the disgraceful incident of 17-year-old Liam Ashley being beaten to death in the back of a prison van.
His own goal aside, O'Connor's question was a good one. If Wilkinson has fallen on her sword, it seems to have been one of those inflatable ones which cushioned her from dropping her other portfolios of Conservation and Food Safety and thereby losing her minister's salary and other perks.
There has been a rash of ministerial resignations during Helen Clark's and John Key's prime ministerships.
But these have all been the outcome of personal failings unrelated to portfolio responsibilities.
Resignations flowing from "culpable" individual ministerial responsibility - the result of action or inaction by a minister's department - is comparatively rare. The previous case was Conservation Minister Denis Marshall in 1996 following the Cave Creek tragedy. He also kept his other portfolios and remained a Cabinet minister. Unlike Wilkinson, Marshall initially clung onto his Conservation job, claiming he needed to fix the "systemic" problems revealed by the inquiry into the collapse of the viewing platform at the West Coast reserve. Wilkinson did not make that mistake.
Marshall's name is forever associated with the deaths at Cave Creek. Wilkinson will likewise be punished for mostly being remembered as the minister who resigned over Pike River.
Marshall's resignation set a precedent which meant Wilkinson had to go if the royal commission found her department culpable even though she was not to blame for decisions made or not made.
There have been murmurings that Paula Bennett should similarly lose her job over the information kiosk-related privacy breach at Work and Income.
Constitutional lawyers, however, argue that a minister is not responsible for everything their officials do or do not do.
Whether a minister stays or goes - either from the relevant portfolio or the Cabinet completely - is a matter of political judgment for the Prime Minister.
The latter is more likely to ask a minister to step down where either the minister has been lax in maintaining sufficient oversight of his or her department. Or if the political price of keeping him or her in the portfolio is too high.
Despite the privacy breach, Bennett remains an asset for National and enjoys Key's full backing.
In short, there are no fixed rules as to when a minister should resign. But it is always obvious when it has to happen.