Our starting-point for thinking about the treatment of the Windrush children is that it must be possible to distinguish stringent checks on those who have no right to be in Britain with just treatment for those who do.  It follows that there should be no objection in principle to the “hostile environment” policy – under which banks, landlords, public employees and others have a responsibility to work with government to reduce illegal immigration.  This take is not universally shared.  The argument being put by some immigration lawyers and campaigners is that the policy should be shredded.  It would be interesting to know from polling what voters think.  We suspect that they agree with us, though we may be mistaken.

But either way, something has clearly gone very wrong when people as entitled to be here as anyone else are denied free NHS treatment, or have lost jobs or homes, or cannot get passports for travel.  Or when Home Office Ministers admit that they cannot be sure whether or not anyone in question has been deported.  Or, to take an example with peculiar application to Parliament, when a cook who once worked in the Palace of Westminster was banged up in the Yarl’s Wood detention and threatened with removal to Jamaica.  It is impossible to quarrel with David Lammy when he describes this as a “national disgrace”.  And the wretched business cannot be, in the title that Dickins considered as an alternative to Little Dorrit, “Nobody’s Fault”.

Amber Rudd can’t evade responsibility for the political mess that has been the Government’s handling of the issue.  But it would be grossly unfair to blame her for policy or operational errors or both that precede her tenure as Home Secretary.  As we pointed out yesterday, former Ministers in the department insist that no Windrush-related problems were drawn to their attention when serving.  None the less, lawyers who support migrants point out that they have been raising concerns for over five years.  Now it is reported that thousands of thousands of landing card slips recording Windrush immigrants’ arrival dates in the UK were destroyed in 2010.

What happened?  It is indisputable that the “hostile environment” policy leaked into the treatment of the Windrush children.  Ministers are ultimately responsible for what happens in their departments.  However, there are degrees of culpability.  Michael Howard once gave the difference between operational and policy matters a famous projection.  Where is the borderline in this case?  It is contemptible to suggest that Ministers will have targeted the Windrush children or anyone else on racial grounds (though doubtless the claim will be made).  But did some Ministers turn a blind eye to the problem?  Were all genuinely unaware of it?  (And if so, how did that come about?)  Was the problem thought to be so small, as the Times has reported senior civil servants as suggesting, as not, in effect, to matter?  Did officials launch a crackdown of their own on illegal migrants in which the Windrush children got caught up, and if so when?  Did the pre-Brexit decision political climate, in which public concern among immigration was higher, and UKIP on the rise, affect the latter’s judgement adversely?  Did they believe that the “hostile environment” policy was an omelette for which it was worth breaking a few Windrush eggs?  Or is the Home Office no more “fit for purpose” than it was when John Reid labelled it so?  (Remember, though: he was seeking to pre-deflect future blame.)

There are three main reasons for projecting these questions and others.  The first is, as it were, a family one.  The Conservatives have a long-standing problem with attracting ethnic minority votes.  The combination this week of the Windrush saga, the Commonwealth summit and the 50th anniversary of Enoch Powell’s Birmingham speech will do nothing to ease it.  The other two reasons have wider resonance.  Second, there is whether the Home Office, for all its policy progress on security and policing, is any better operationally than it was in Reid’s day, at least when it comes to migration and border control.

Finally, the questions throw themselves wider than the Windrush children and into the Brexit negotiations.  The European Commission, other EU government and some MEPs are already seizing on what has happened to ask whether Britain will treat EU citizens fairly in future, and whether our systems are up to doing so.  A quarter-competent Opposition would be running with this ball – casting about for leaks, briefing stories, raising questions, tabling debates.  As Shadow Home Secretary, David Davis succeeded in helping to bring down Charles Clarke after it emerged that over a thousand foreign prisoners had been freed without being considered for deportation.  But where the Conservatives had Davis, Labour has Diane Abbott.  True to form, she is demanding resignations, not asking questions.

There is cynicism about inquiries – and no wonder, after the one into child abuse was grotesquely over-inflated.  Others crawl towards necessary conclusions after years at staggering cost, like the one into Bloody Sunday.  The Home Office Select Committee will surely soon be all over Windrush.  But there is a good case for a inquiry, headed up by someone who knows how the wheels of Westminster and Whitehall grind and clash, into the questions we ask above, and others.  It would be tasked with drawing up lessons for the future treatment of EU nationals post-Brexit.  It would not always sit in public: the risk of it turning into a circus would thus be reduced.  Its mission would be to get at truth rather than get at Ministers – or anyone else.  There is a future as well as a present need for it.