One charming feature of the Brexit process has been the way that the minutiae of treaties has entered the language of our politics. In the immediate aftermath of the referendum, the artefact of power was Article 50. As the row over the Northern Irish Protocol drags on, we’re now getting to know Article 16.

First, the Government seemed to be building up to trigger it. Both privately and publicly, the briefing was that it would have to be done if decisive change was not achieved by last November.

Yet by December, the fight had gone out of it. We’re still not sure why. One plausible theory, advanced by Dominic Cummings, is that David Frost and his team had a coherent strategy for when and why to trigger Article 16 (and crucially, what to do afterwards), but didn’t think the Prime Minister had the will to see it through.

Now Frost is gone, and this constitutional One Ring has been passed to Liz Truss. Once again there is bullish talk of actually wielding it. (And instead of a Foreign Secretary, Ulster would have a Queen!)

For Unionists, this newfound resolve might be a cause for hope. The Protocol needs to change, and the experience of the past few years is that if you tell the European Union in advance that you won’t do anything if they don’t make concessions, it quite understandably doesn’t make concessions.

And for all the spluttering on the European side, there is a coherent prima facie case for the Government triggering Article 16. It sets out that either party may take unilateral action in the event of  “serious economic, societal or environmental difficulties that are liable to persist, or to diversion of trade”. Brandon Lewis is right to say that these conditions have been met.

Moreover, there should be no talk of the United Kingdom ‘refusing to honour what it signed up to’. Article 16 is literally part of the negotiated agreement. The wisdom of putting a “pull in the event of diversion of trade” killswitch on a treaty that was always definitely going to divert trade is open to question. But the switch is there.

(By contrast, the EU threatening to tear up the entire agreement if the UK does trigger Article 16 is very much a party refusing to honour what it signed up to, to a degree which borders on lèse-majesté – or a continuation of the attitude which saw the EU’s initial negotiating stance compared to that taken by the European imperial powers towards China in the 19th Century.)

But having this decision in Truss’s hands rather than Frost’s does change the calculation in a potentially dangerous way, for one simple reason: she is a contender for the Conservative leadership, and he was not.

This does not mean that the Foreign Secretary will conduct the negotiations with that fact solely or even uppermost in mind. But she surely cannot help but factor it into her calculations. Being seen to roll over for Brussels will do her prospects no good; standing up to the Eurocrats has seldom damaged the standing of a Conservative politician with the party selectorates, in the Commons or the country.

Yet if Cummings’ analysis is correct, the underlying conditions which informed Frost’s calculations haven’t changed. There is no obvious reason to believe that the Government, already facing a looming cost-of-living crisis, is better prepared for a serious breakdown in EU relations – and attendant disruption of Channel trade – than it was just a couple of months ago.

But Johnson may, nonetheless, have placed this instrument in the hands of someone with a much stronger personal motivation to wield it. He’d best make sure there’s a plan for if she does.