Lord Frost is Minister of State at the Cabinet Office and former chief negotiator for Brexit.

Policy Exchange has performed a huge public service in publishing today Roderick Crawford’s meticulous analysis of the so-called “Joint Report” of December 2017.

He has written a piercing analysis which, for as long as the issues raised by the Protocol on Ireland / Northern Ireland are not yet settled, will be of more than purely historical interest.

I may differ from Roderick on a few points of detail, but not on the overall assessment: that the Joint Report, so-called because it was an agreed document between the UK and the EU, is arguably the text that has done most to shape the terms of this country’s exit from the European Union.

As Special Adviser to Boris Johnson when Foreign Secretary, I was a close observer, rather than a participant, during the period covered by this document. I nevertheless have acute memories of it.

As the Report circulated within government that December, it was immediately clear to us that a crucial pass had been sold in agreeing — unless an alternative was agreed with the EU, which it clearly would not be — to “maintain full alignment with those rules of the Internal Market and the Customs Union which, now or in the future, support North-South cooperation, the all island economy and the protection of the 1998 Agreement” (paragraph 49 of the Joint Report).

Although efforts were made internally to persuade us that “alignment” really meant “equivalence” or “approximation”, we could see that that was not so, and that the effect of this commitment would be to keep the UK in the customs union and much of the single market and thus to destroy the prospect of a meaningful Brexit. This indeed turned out to be the outcome in the initial version of the Protocol from November 2018, via the famous “backstop”, an agreement which Parliament consistently refused to approve.

As I fielded furious calls from Brexiteers that December week, I had two thoughts in my mind. First, “if I resign over this, how will I ever explain what it is all about?” That was a valid question at that point. When all the politics were about how we got over the “sufficient progress” threshold to further talks, this point on Northern Ireland would seem to many like a technicality.

By July 2018, this was no longer the case. The linkage between Ireland, the fanciful “Chequers” proposals, and the inexorable logic on which the then Government was embarked was all too clear. It has been with us ever since.

My second thought was “how did we ever come to agree to this?” We now know, from Irish and other EU sources, that the EU was asking itself the same question. Close observers could see that the North-South dimensions of the Belfast Agreement had been prioritised over its other dimensions, that the Report would not command any support from the unionist community, and that the British Government’s agreement to these provisions was wholly unexpected.

My answer is three-fold. First, we had drifted into accepting the EU’s view that the only way to ensure no “hard border, including any physical infrastructure or related checks and controls” (para 43 of the Joint Report) was for the laws on either side of the border to be identical. This ignored the fact that there already was, and is, an international border, an open one, with different currency systems, laws, taxation, and many trading rules on either side.

Second, I do not think we had made the necessary mental shift from being a member of the EU to negotiating exit from the EU. While Olly Robbins was doing his level best to negotiate exit, UK diplomats were trying to participate in EU institutions as if we were a normal member state. Our collaborative instincts from 45 years of membership meant that we were too slow to adopt a robust enough negotiating position. It is very clear that the EU did not make the same mistake, and it was explicitly to reset this psychology on our side too that we withdrew UK diplomats from most EU meetings from August 2019.

Third, it is only fair to point to the extreme weakness of the UK Government after the June 2017 election, both in Parliament and in the lack of consensus amongst its key members about how and perhaps even whether we should be exiting the EU at all. The criticisms made of the Joint Report must be tempered by the difficult circumstances in which the negotiators found themselves, compounded as they were by the EU’s desire to maximise their leverage on Northern Ireland.

When Johnson returned, as Prime Minister, in July 2019, and I returned as Chief Negotiator for Brexit, we inherited that Parliamentary weakness too. Nevertheless we were able to re-establish a clear purpose for the Government and to reset the balance on two crucial points, set out in the Prime Minister’s letter to Donald Tusk of August 19.

The first was an unequivocal commitment to the Belfast Agreement and a clear statement that the backstop risked undermining the “delicate balance” between its three overlocking strands.

The second was an explicit disavowal of the commitment to “alignment” in paragraph 49 of the Joint Report.

Despite this, in the short window of the next two months, we inevitably still operated within the intellectual and political framework set by the Joint Report. Our negotiating leverage had been cut away by the Benn-Burt Act, which made it impossible for us to leave the EU without a deal, and there was even an increasing worry that it might turn out to be impossible to deliver on the referendum result at all.

Nevertheless we got a deal that took the whole of the UK, including Northern Ireland, out of the EU. The deal restored genuine agency to us for the future, by removing the backstop, which would have locked the whole country in the customs union and much of the single market and given the EU the key.

But we could not in the end escape the EU’s insistence on imposing its customs and goods rules in Northern Ireland. The best we could do was include mitigations and balances in the new Protocol — and, crucially, given all these uncertainties and political novelties, insert the principle that the functioning of the Protocol beyond 2024 required the explicit consent of the Northern Ireland Assembly.

We knew, as did the Irish Government, that this new Protocol would require immensely sensitive handling. We understood that the East-West dimensions of the Northern Irish economy are in any circumstances vastly more important than its “all island” dimensions — and that the former not the latter were the economic lifeblood of the province.

We knew, as some in the Irish Government would privately concede, that the balance between the three strands of the Belfast (Good Friday) Agreement had been upset by the approach taken in the Joint Report; and that the risk was that the EU’s approach to the Protocol would not be consistent with the explicit commitment to protect the Agreement, in all its dimensions.

Unfortunately the operation of the Protocol has not been adapted to these underpinning realities. It has begun to damage the thing it was designed to protect — the Belfast (Good Friday) Agreement. The insistence of the EU on treating these arrangements as like any other part of its customs and single market rules, without regard to the huge political, economic, and identity sensitivities involved, has destroyed cross-community consent well before the four-year mark.

We also have the lived experience of aspects that are simply unsustainable in the long-term for any Government responsible for the lives of its citizens — like having to negotiate with a third party about the distribution of medicines within the NHS. That is why we must return to the Protocol and deliver a more robust, and more balanced, outcome than we could in 2019. I hope the EU will in the end join us in that. And in so doing we will, I hope, finally move beyond the intellectual framing that Crawford so ably describes.