Elevated to an art form by Henry Kissinger, “constructive ambiguity” has long had its uses in diplomacy. By leaving vague the meaning and consequences of contentious initiatives that might otherwise keep rival negotiating teams implacably divided, it permits navigation around competing “red lines” and towards agreement. It helps both sides assert – and perhaps believe – that they have won. Among the achievements claimed for constructive ambiguity is the Belfast (Good Friday) Agreement of 1998.

But constructive ambiguity cannot be the goal. It is merely a tactic – not a strategy, a tactic – for getting from ‘A’ to ‘B’ without dynamiting the jagged granite boulder blocking the path. That obstacle remains, nevertheless. And, as time goes by, a layer of mythology develops not only over what was actually agreed but what was the intention of what was agreed. By such myth-accretion has Northern Ireland’s peace process made Brexit so much more complicated.

According not just to instant experts like Joe Biden but also to John Major and Tony Blair, who were key participants in the path to the deal, a central goal of the Belfast Agreement was to cement peace by effectively removing the border between Northern Ireland and the Republic of Ireland. Hence in the service of this peace-over-bombs imperative came Theresa May’s “backstop” and thereafter Boris Johnson’s re-worked Withdrawal Agreement that secured the UK’s negotiated departure from the EU.

There is, in fact, nothing in the Belfast Agreement – so often cited, so little read – that states, or can even be interpreted as stipulating an open border between Northern Ireland and the Republic. There is mention of cross border co-operation and bodies that remain unchanged by Brexit, but on the importance of an open border, not a peep. Major, Blair, or anyone else involved in the 1998 agreement, are entitled to remember their role and what they intended through it however they may. But the historical – and the legally-binding – records are less expansive. We are being led into an even greater thicket of constructive ambiguity now than existed back in 1998.

We print the legend, nonetheless. But the truth is that in order to maintain the open border brought into being as a consequence of shared EU membership (and not through any clause of the Belfast Agreement – that document should rightly be credited with leading to the removal of anti-terrorist checkpoints, not the absence of regulatory checks) Boris Johnson’s government has been engaged in its own constructive ambiguity ever since it agreed to the Northern Ireland Protocol and the Withdrawal Agreement.

These agreements ensured a border separating two parts of the UK (inexplicably this genuine innovation has not been declared a breach of Belfast Agreement). Whether interpreted generously or meagerly, this new border will be less open than the one demarcating Northern Ireland from the Irish Republic. The ambiguity over what will be the extent of the NI-GB border’s openness was convenient back in October when what amounted to Johnson’s Brexit “get out of jail” deal was agreed with the EU. But eleven months on, the ambiguity requires clarity because Michel Barnier has been explicit about Brussels regarding the new Irish Sea border between Britain and Northern Ireland as a very hard border indeed.

Long in, or feigning, denial, Johnson’s cover is blown. His first response was to reassert the British government’s right to override an international agreement. To appease anxious backbenchers, this has now been amended to handing that honour to MPs directly to determine (with a promise to simultaneously pursue arbitration through the EU-UK Joint Committee).

Barnier has certainly been brutal. But it really will not do for the British government to play the innocent dupe. It is preposterous to suggest that back at the time of signing the deal Whitehall’s lawyers did not spot the extent of how it created regulatory and bureaucratic impediments, let alone the enormity of the tariff and state aid implications, between Britain and Northern Ireland.

How did this failure of statecraft happen? Theresa May’s solution (effectively a Brexit-in-name-only in which the UK would continue to be widely bound by EU regulations but no longer able to shape them) having been repeatedly voted down in the Commons, her successor was in a bind. Faced with the machinations of Speaker Bercow and unhelpful parliamentary arithmetic, there appeared no easy route out than to either abandon Brexit and implode the Conservative party or sign up to the deal Johnson concluded with the EU. Remainers apoplectic at the tricks Johnson now plays may usefully reflect upon their role in contriving this state of affairs. At the time, the prime minister knew the cost was deferred rather than waved. He thus signed the Withdrawal Agreement with a lie and a prayer.

The lie lead him down the path upon which his government now finds itself. The prayer was that the Withdrawal Agreement’s harm to the unity of the UK would be corrected through the successful negotiation of a UK-EU free trade agreement.

Boris Johnson signed the Withdrawal Agreement with a lie and a prayer.

Perhaps that rabbit will yet be pulled from the hat, in a turnaround not seen since Neville Chamberlain arrived in the House of Commons to report on preparations for war only to be interrupted midway through by a note saying the Fuhrer was anxious to talk things over with him in Munich. That, incidentally, is not a happy precedent. To start from a position where only a successfully concluded free trade agreement could save the UK from self-amputation was to invite Brussels to demand everything and concede nothing in the ensuing talks. Can politicians really be surprised that this has duly been Barnier’s approach?

In Westminster and beyond, there is considerable anger – much of it justified – at the way the British government has communicated its intended “specific and limited” breach of international law as envisaged in the Internal Market Bill. As far as the world is aware, a solemn deal was concluded under the sacred agency of international law and now the British want to welch on it. Who could trust this perfidious Albion ever again?

At the very least, it would have been better PR had Johnson’s comms team put the horse before the cart by claiming that it was the EU that first reneged on its “best efforts” to find a solution and had instead fallen back on the most Carthaginian terms imaginable of EU legal “direct effect.” Put this way, the UK’s Internal Market Bill was a response to this breach of international good faith, if not law, and was not the creator of the discord.

Various theories are advanced as to this failure of communication. For instance, the FT leaked the story before Downing Street had got its story straight. But there is more to it than that.

Downing Street has been spinning different stories to different audiences ever since the Withdrawal Agreement was signed. Reality has caught up with this double-dealing.

Then again, perhaps duplicity is the wrong charge. Downing Street’s inconsistent message can also be seen as a consequence of ambiguous thinking. Could this be worse than playing different audiences off against each other in a policy of divide and rule? For it implies the ambiguity has all along lacked sufficient creativity.