The Home Office and the Treasury have a fraught history of squabbling over immigration. Home Secretaries place primacy on questions of border integrity and control, and know that various of their predecessors’ careers have been destroyed by failing to live up to popular expectations and their own promises on the topic. The Treasury, meanwhile, believes – both due to its own analysis and its regular contact with large businesses – that their colleagues on Marsham Street are imperilling economic growth with an obsession with constraining immigration at any cost.

The balance of power within government between these two positions ebbs and flows. In the Cameron years, the “tens of thousands” net migration pledge held – at least rhetorically, if not practically – as a form of uneasy truce. The two occupants of Downing Street were instinctively more relaxed about immigration than Theresa May, but they recognised that any prospect of electoral success required at least some presentational effort to square away the issue.

Nonetheless, as the target was repeatedly missed it became a source of friction in both directions, with the Treasury wondering aloud about relaxing an unmet goal, perhaps by exempting students, and the Home Office pointing to the rise of UKIP as a deterrent against any attempt to abandon it. Everybody knew that the net migration pledge was essentially unfulfillable, at least while the UK economy grew and EU membership required free movement, but the already sensitive topic was becoming harder and harder to handle. It duly helped to sink Cameron’s renegotiation, and then contributed in no small part to his defeat in the referendum.

Traditionally the Treasury has tended to have more influence in Number 10 than the Home Office. Chancellors hold a more mighty Great Office of State, they live next door to the Prime Minister, and they control the purse strings. Added to which, the growth of the rights which the Treasury claims over other departments means that its officials often end up going to Number 10 in various capacities, both operational and policy.

Given that context the immigration battle within government normally involves the Treasury pushing for more, with a sympathetic hearing from the Prime Minister, and the Home Office battling for less, waving the polls as a cudgel.

However, this is 2018 so everything is upside down and back to front – hence the peculiar sight of a Home Office-dominated Number 10, occupied by a Prime Minister personally committed to the “tens of thousands” pledge, trying to persuade a more business-minded Home Secretary to be tougher on immigration than he would instinctively like.

One can see in the way that May prioritised immigration apparently above everything else including the costs of EU regulation in her Brexit negotiations that she has no intention of shifting her position. Where David Cameron once joked that he and she were the only two supporters of the net migration target in government, she now seems like the only one. Indeed, it has fallen to a frustrated Downing Street to clarify today that this is still the official policy, after the Home Secretary told the BBC “there’s no specific target.”

I wouldn’t expect this unusual state of affairs to persist for very long, though; the traditional Treasury vs Home Office divide will likely reassert itself in time. Brexit offers the chance to draw some of the fury out of the immigration debate, as can already be seen by a softening of public opinion now that people at least believe the policy will be under their democratic control. As that happens, I suspect we will see more intense inter-departmental scraps about it, as ambitious ministers bid to appeal to different segments of the electorate – in other words, returning the topic to one of normal democratic politics.