There is something wonderfully appropriate that we are leaving the EU at 11pm UK time on March 29, 2019 - because that’s when it will be midnight in Brussels.
We’ll be subject to European rules - even those that determine the time - to the very end.
But what’s really important about the government’s proposed amendment to its own EU withdrawal bill, which specifies that precise hour as the moment of rupture, is that it shows quite how fearful the Prime Minister is that no one really believes her when she says Brexit means Brexit.
She has written the timetable for Brexit into British law to prove to both the rest of the EU and her suspicious Brexit-loving colleagues that we really, really, really are leaving!
But here is the truth she knows and hates: Brexit might not actually mean Brexit - as the author of Article 50, the framework for our divorce negotiations, pointed out this morning.
Lord Kerr, former head of the foreign office made it crystal clear on Friday that the UK can change its mind about leaving - with no financial cost - at any time before 11pm March 29, 2019. Although we might feel a bit foolish if we suddenly said it had all been a misunderstanding, the rest of the EU could not evict us.
Now I am not remotely saying we should change our minds. The referendum result matters. I am simply pointing out it’s an option.
And the fact that we have not yet passed the moment of no return may well explain why our negotiations to leave have been so slow and painful, and have been characterised by very little compromise from Michel Barnier and his EU negotiating team.
In fact MPs from the Brexit select committee met him mid-week and were shocked when he made clear he expected all compromise and sacrifice to come from Britain, not the rest of the EU.
This is a rational negotiating stance from him if he knows we can change our minds: most of the rest of the EU does not want the UK to leave, and their best hope of persuading us to stay is to make Brexit as expensive and disruptive as possible.
And this in turn explains why the Brexiteering ultras remain profoundly concerned that their dream of independence may yet be frustrated.
It is also why they are desperate to make a no-deal Brexit plausible and palatable - because if it’s not, the British people might decide that the door they chose wasn’t a clean exit with no way back but a revolving one.