The Prime Minister did the right thing yesterday in quickly accepting Maurice Williamson's resignation. He also made appropriately strong comments about the minister "crossing the line" when he phoned the police after wealthy businessman Donghua Liu was arrested on domestic assault charges.
But John Key's swift response could not paper over several troubling aspects of the incident, not least the belief of a man with 27 years' parliamentary experience that he could approach the police in this manner. Or the fact that this is a far from isolated instance of a member of Mr Key's Government displaying so grievous a lack of judgment that it raised questions about their personal ethics.
Yet the lessons arising from this string of transgressions seem not to be being learned.
The Cabinet Manual is clear about ministers interfering in police investigations. It says: "Following a long-established principle, ministers do not involve themselves in deciding whether a person should be prosecuted or on what charge." That principle has been strongly reinforced in the courts, notably in a British Court of Appeal judgment that concluded the police were "answerable to the law and to the law alone". They must be able to focus on their operational responsibilities without political interference or pressure.