It was always likely that outrage at the treatment of the Windrush children would morph to criticism of the “hostile environment” policy…to suspicion of checks on illegal immigration per se…to opposition to the Government’s net migration policy…to objection to almost any reduction of immigration at all.  That is roughly the progress demonstrated yesterday by the latest outing from Sayeeda Warsi and the Observer.

Not all the components of this chain of thinking are mistaken.  For example, this site has never been a fan of the net migration target: see this from Mark Wallace from as long ago as 2014.  And what has been happening to the Windrush children is deeply wrong.  But the starting-point of much of the Left’s approach to the outrages has been that wider checks for illegal immigration must be followed by severe injustices.  So those checks must be abandoned.  This seems to be the position of Jeremy Corbyn and Diane Abbott.

One report this morning suggests that senior Conservatives believe that the scandal will cause no long-term damage to the Party.  It is doubtless true that there are significant parts of the country outside the M25 belt, and its urban equivalents elsewhere, where it has made almost no impact at all.  Liberal London and the provincial Britain aren’t the same thing.

But Windrush will have had an impact on parts of the rest of the latter and, to turn themselves into electoral winners, the Tories need to win lots of metropolitan seats in any event – and up their dismal showing among ethnic minority voters.  The Party needs to make an impact in Brentford and Isleworth as well as Bishop Auckland.  Winning in both would be a modern equivalent of what Margaret Thatcher did in the 1980s – aided, admittedly, by a split on the Left.

Labour’s main response to Windrush has been to call for Amber Rudd’s resignation.  This is weird for two reasons.  First, because problems in the Home Office’s treatment of the Windrush children obviously pre-dates her tenure at the Home Office.  Second, because Theresa May herself was Home Secretary during that period, and is a more potent target for Labour.  But, as its handling of the missile strikes on Assad reminded us, Corbyn leads a lousy Parliamentary opposition.

Giving the Opposition advice is not exactly ConservativeHome’s vocation.  But it is hard to understand why Labour, and some Conservative MPs, are not pressing the case for an independent inquiry.  The thought chain that we set out at the start of this piece is cumulatively mistaken: it must be possible to have tough checks on illegal migration that don’t impact unfairly on other people.  Such will surely be the position of most voters.

The question is why the “hostile environment” policy mutated in such a way as to blight the lives of people entitled to be here – and who have been living in Britain for many years.  Rudd has been slated for her handling of the crisis.  Fair enough.  But she cannot exclusively be blamed for it, given how far its origins run back.  Indeed, the tightening-up of checks on illegal immigrants began under Labour.

The case of an inquiry is far from retrospective.  The Home Office must implement a system for the registration of EU nationals.  Windrush has already been seized upon by the other side of the negotiating table in the Brexit talks.  There will be renewed pressure for the ECJ to be the final arbiter.  But the department’s future task stretches wider – namely, to implement and administer whatever the Government’s future migration policy turns out to be.

To do so effectively, it needs, not to coin a phrase, to be “fit for purpose”.  It won’t be if there’s no understanding of what went wrong with Windrush.  And for that we need an inquiry to find out more.