Although the Article 50 process settles the terms in which a departing member of the European Union leaves the bloc, and sets out the broad outline of the future relationship, it does not contain a long enough period of time to negotiate a full-fledged trade agreement between the EU27 and the departing nation.

And, again, because of the time, that transition period will have to look like membership of the European Union, but without voting rights or other say in the institutions of the EU.

That’s the argument that Theresa May set out in her speech in Florence on 22 September last year and one that the EU27 has unanimously accepted today. But what should be a positive step is instead being greeted by sounds of dismay from Brexiteer ultras.

In a way, the growing row over the length of the transition after is your typical Brexit story: pro-Brexit MPs with little grasp of the issues involved are causing a fuss for no good reason other than ignorance or fanaticism. (And if you don’t believe me, take the following pro-Brexit commentators: Reaction editor Iain Martin, and the Spectator’s James Forsyth.)

Except: actually the Brexiteers have a point this time. They suspect that May is trying to pull the wool over their eyes, and they’re right. And they fear that the transition will go on forever, and there is at least a possibility that could turn out to be right, too.

On the former: it’s not clear if the Prime Minister is fooling herself or just trying to fool other people, but, in any case, the United Kingdom’s new relationship with the EU is not going to be ready to be implemented by 31 December 2020 when the proposed transition comes to an end. It is highly likely that the United Kingdom will end up asking for an extension on the extension. The difficulty from a British political perspective is that 31 December 2020 is the end of the current EU budgetary period. EU budgetary periods last seven years, a long time for the United Kingdom to be in transition if 31 December 2020 is not enough time.

So the fear that the transition will last past its advertised date is not unreasonable. And nor is worrying that transition will simply go on forever.

Thanks to the snap election, the Article 50 and electoral timetables are now dangerously out of sync as far as the government is concerned. We are now due to leave the structures of the EU for real on 1 January 2021, the last full year of the current parliament. In an ideal world, in the final year in the run-up to an election, particularly when the outcome is uncertain, the government would have a free year to concentrate on its re-election, not on navigating the post-Brexit position. (Had May not gone for an early election, ending the transition shortly after the 2020 election would have been quite good as far as navigating the election goes.) The sensible time for the transition to end would be 2024, midway through the next parliament, so the government could minimize the electoral fallout if the immediate exit goes badly. But that also means risking handing control of Brexit over either to Labour or to a Labour minority that has reached some kind of accord with the various pro-Remain forces in parliament. And given all the evidence that the United Kingdom is getting more pro-Remain with time, the longer the transition goes on, the greater the chance that it simply is no longer in the political interest of the sitting government to leave.

None of which is to say that Brexiteers aren’t asking for the impossible in wanting a bespoke or no transition after 29 March 2019, or that a short transition doesn’t increase the chances of a bad Brexit and thus increase the chances the United Kingdom will rejoin in short order. But it is to say that their fears aren’t entirely incorrect.