As Christopher Howarth warned on Tuesday, the nasty thing about “transitional” arrangement with the EU is that they have a habit of being permanent. Much like the temporary introduction of income tax during the Napoleonic Wars, or the thrice-cursed Barnett Formula, things that are meant to only last a short while tend to stick around for perpetuity, bedevelling any and all attempts to move on to what was meant to be the permanent state of affairs.

This should give us pause for thought before steaming into a supposedly temporary bridging arrangement with Brussels. Not only could the reality be longer-lasting than the theory, but voters would be justifiably sceptical and entitled to wonder if the contents of such a deal really do what it says on the tin.

As is so often the case, this would be particularly awkward on the topic of immigration. Of the three things Vote Leave wanted to “take back control” over – our laws, our money and our borders – a transitional arrangement could conceivably do at least a partial job on the first two. There could be limits on the introduction of new EU legislation during a transition, though that wouldn’t do anything to solve the numerous and costly pre-existing body of EU law. Our membership subs might conceivably be reduced to recognise that we were on our way out of the club.

Neither of these would amount to proper Brexit – which is why a transitional arrangement that became permanent would be totally unacceptable. But they would at least involve a little bit of progress. A transitional arrangement wouldn’t – couldn’t – do anything to change the situation on immigration one iota, though. Free movement would remain in place, and our borders would remain open.

The prospect of entering a long-lasting “transitional” limbo is unappealing enough. Leave voters would be justifiably angry at what would amount to a fudge at best. But consider the continued loss of control over immigration as well, and it becomes clear that it wouldn’t be tenable at all.