Theresa May’s conference speech yesterday can be read as a part of her leadership election campaign, a signal that she wants Britain to leave the EU, or both together – which is how much of the Westminster Village has duly interpreted it.  But there is a further dimension to the political background.  The Home Secretary is under pressure from her Cabinet colleagues to take students out of the immigration figures.  Sajid Javid, Philip Hammond and, above all, George Osborne have all been reported to oppose May’s position.

It was a mistake on the Home Secretary’s part not to take the precaution of inserting the usual tribute to the contribution that migrants make to Britain in her speech – partly because to do so would have been prudent politics (if you’re making a bold speech, you should guard your back) and partly because it would have been right to do so.  However, the absence of these usual bromides was a sign that she wanted to dispense with the conventional formalities.  Her speech was primarily a serious piece of argument, not a text crafted for applause lines.  This was so last year, when the commentariat applauded it to the rafters, and mocked the address from Boris Johnson that followed.  And it is so again this year.  That the commentariat have panned it and praised the Mayor of London instead shifts this fact not an inch.

May was making a three-part case.  First, that – as the most comprehensive study of the evidence has found – the net economic gain from the high levels of immigration that we have had is, as she put it, “close to zero”.  Second, that these are not compatible with social cohesion and, third, that the number of migrants admitted should be in the tens of thousands and not in the hundreds of thousands.  And the further you live from within the M25 (psychologically, if not physically), the more likely you are to agree with her.

George Osborne, Jeremy Corbyn, Fraser Nelson, James Kirkup of the Daily Telegraph, Simon Walker of the Institute of Directors and –  for that matter – myself are doubtless all different in many ways, but we have at least two things in common, other than being men.  First, we will all be in roughly the top three per cent of earners.  And, second, we all work in the pullulating, immigration-rich, culturally dazzling, poverty-afflicted, liberal-inclined greatest city in the world.  We are all social liberals – up to a point – and more likely, like most of those on similar incomes, to experience the pluses rather than the minuses of mass migration.  For those in the top earning decile, it is more likely to mean French nannies and Polish plumbers than, say, our children being consigned to the poorer-performing state schools.

This leaves May exposed – to the Vice-Chancellors; to her Cabinet colleagues; to parts even of the centre-right press; to the groupthink of the London zeitgeist and, above all, to the failures of her own record and the unworkability of the Government’s own target.  But all that does not add up to her case being wrong.  As she pointed out, the Government has had some successes in controlling numbers (consider the crackdown on student visas) and could have even more.

That, of course, will hinge on Britain being able to control its own borders, which cannot be done without leaving the EU…which leaves the Home Secretary with only one course to take in the coming referendum campaign if she wants government action to match her rhetoric.  In the meantime, at least three of her Cabinet colleagues want to shift her policy, and at least one wants to take her place.  I refer to Nicky Morgan’s Tory leadership aspirations.

This makes May dependent on the man who is speaking in Manchester as I write this article.  The lump of David Cameron’s speech that was pre-briefed were his words on housing.  It is not a policy area which he had any responsibility for before becoming Prime Minister, but the same cannot be said of immigration.  Cameron is a former Home Office SpAd.  He understands the issues.  He must back his Home Secretary up.