Now is the time, at the end of what has been a terrible week for the Government, for what Americans call a reality check. There are many questions of detail that will be investigated by the inquiry set up by Gordon Brown. There are important implications for policy on the national children's register that is supposed to "go live" next year, and on identity cards further down the line. But the big political question posed by the case of the missing HMRC discs is this: is there any reason to suppose that a Conservative government would be any more competent in the administration of public services than the present incumbents?
The short answer is no. The opinion-poll evidence that David Cameron and George Osborne are now regarded as more competent than Mr Brown and Alistair Darling must be accounted an overreaction. Of course, Mr Cameron made a reasonable show of righteousness in the House of Commons this week. In truth, the intensity of Gordon Brown's embarrassment concealed the fact that there was little sensible that the Leader of the Opposition could say. The danger for Mr Cameron was that he would muff his big moment: the press gallery was full and everyone was expecting great sport. So when the Prime Minister pointed out that the Conservative Party at the last election proposed £660m in savings in "data processing" at HM Revenue and Customs, Labour MPs roared their delighted approval.
Mr Cameron took the high rhetorical ground, saying, with emphasis, that "to try to blame the Opposition is pathetic". It was a put-down of Blairite style that parried the attack and rallied his own side, but it was hardly an answer. Mr Brown had a good point. If – and it is not clear to what extent this is true – cost-cutting was a factor in the foul-up, then surely the pressures would have been greater under a Conservative government.
The question of cost control is, in any case, only part of a larger issue: that of how to manage efficient public services. Mr Cameron, it is often observed, is typical of modern politicians in having no experience of management. His elevation to the leadership was hailed as the triumph of special adviserdom.
David Davis, the shadow Home Secretary, on the other hand, is an example of that increasing rarity: a politician that has had a proper job; in his case as an executive at Tate & Lyle. Yet few politicians of whatever party take public administration seriously. There may be a select committee with those words in its title – indeed, earlier this week Ed Miliband, minister for the Cabinet Office, admitted that most ministers were "undertrained" for their jobs, which was a polite way of saying "not trained at all".
The last politician to take up the cause was Al Gore. When he ran for the vice-presidency in 1992, his big idea (apart from the environment) was "Reinventing Government". His researchers exposed some of the wilder excesses of military procurement – screws for which the US taxpayer was charged hundreds of dollars – but the programme rapidly faded from view when the election was over.
So Mr Cameron can wallow in Mr Brown's discomfort now. He can bat aside serious points made by the Prime Minister because the music just happened to stop when Mr Brown was nowhere near a chair. The Conservatives will benefit because Labour's reputation for competence has, somewhat unfairly, been lost in the internal mail.
But unless the Conservatives start doing some serious work on how to transform the culture of inefficiency and getting-by that suffuses so much of the public sector, their turn to be apologising for the inexcusable will come soon enough.