It was 1974, and I was in the press room in Stormont, watching in horror as the mile-long driveway filled with protesting farmers.
The power-sharing Executive was already on its last legs after several weeks of loyalist workers' strikes and IRA attacks, but this example of literally grassroots opposition delivered the final blow.
But opposition to what? The general opinion among the journalists in that room was that the creation of a cross-border Council of Ireland was a bigger source of unionist ire than the sharing of government between them and the nationalists of the SDLP.
Politically, the SDLP could not enter such a government without an all-Ireland dimension. And so we got 20 years of violence, while Seamus Mallon's "slow learners" who now sit on the new Executive came to grips with reality.
However terrible it all was, one assumed the lessons had been learnt. The response to Brexit suggests that the lessons may have been forgotten. It was always a bit depressing that the cross-border institutions for which so much blood was spilt were largely regarded as irrelevant after the Good Friday Agreement. Now, suddenly and unexpectedly, they are absolutely relevant and possibly the best chance of preventing the worst political and economic damage from Brexit. But it's still as if they didn't exist.
One alarming estimate is that damage to the Republic from Brexit will be six times greater than for any other EU state. It is reasonable to assume the damage to Northern Ireland will be greater still. There is convincing evidence that the only way to develop the private economy and reduce dependence on public spending is for the North to replicate some of the South's success in attracting foreign investment.
The UK's 30pc share of FDI into the EU seems bound to decline, even with a freer hand to provide incentives. Northern Ireland's minuscule share will also decline.
Its reliance on the British Treasury will continue but, if the pessimists are even half right, the effects of Brexit will mean reductions in public spending in the medium to long term. This at a time when the Republic's own incentives for foreign investors are under severe, probably terminal, threat.
Yet here is the first opportunity for Belfast and Dublin to consider how the whole island might maintain an advantage in securing foreign investment, with one area inside the EU and the other not. But don't expect that to be enough on its own to get everyone together to minimise the impact. The politics must be right.
I use the names of the two cities because there are two administrations, even though only one is a sovereign government. That government has invited "political parties" to next month's civic dialogue, as though no Northern executive existed.
In an ideal world, the Irish Government might quietly prepare the ground with the Northern Executive and wait to make its case about the island of Ireland when the terms of a UK-EU arrangement became clear.
The peace process is in many ways a European success story and there will be some in the EU 26, although not all, who will want to help preserve it. There are precedents of a sort; "variable geometry" for regions and special arrangements for Finland, but all would depend on the final deal between the UK and EU.
But it is not an ideal world. Both jurisdictions will have to act now to make the island as a whole more economically efficient. This was one of the theories behind the all-Ireland institutions, but narrow self-interest limited progress in energy, education, health, communications, investment and transport (to name but some).
There is nothing like the prospect of hanging separately to encourage hanging together and this is the choice facing the island. The institutions of the Good Friday Agreement fit the bill. They allow the two governments, sovereign and devolved, to meet as equals, which is the only hope of joint action at all. Their scope can be extended by agreement, and there is also the British-Irish Council, which includes the Scottish and Welsh administrations and has a secretariat in Edinburgh.