In the years before and after the Belfast Agreement, relations between Ireland and Britain were marked by levels of trust and co-operation that would have been unthinkable for much of the previous century. That was true at political and official level, where close working relationships as well as shared views on key policy issues allowed the two capitals to find common cause within the EU and elsewhere.
The bond between the two neighbours would have been hard to imagine at the height of the Troubles and the normalisation began to be taken for granted.
But the assumption that Northern Ireland, where the principle of consent was well established and whose peace process Dublin and London steered as joint custodians, could no longer drive a wedge between the two capitals was shaken by Brexit. And the tensions created by the UK's vote to leave the EU in 2016 have only intensified in the intervening years. Commenting this week on the deterioration in the relationship as a result of the dispute over the Northern Ireland protocol, Taoiseach Micheál Martin said "unilateralism flies in the face" of the approach that delivered the peace process, which involved "both governments working hand in glove and together". Minister for Foreign Affairs Simon Coveney said the working partnership approach adopted in the past to deal with contentious issues in the North was "absent at the moment".
The Government has a delicate balancing act to perform. The outrageous British threat of unilateral abandonment of the protocol, a move motivated far less by concern for the interests of Northern Ireland than by the narrow political concern of Boris Johnson to tend to his Conservative right, cannot go without a firm response. The European Union says it is open to constructive ideas for making the protocol less onerous but has yet to hear such ideas from the British side. At a certain point the EU will have to make clear that unilateral action from London would provoke a reaction that could prove extremely damaging to the British economic interests.
For its part, the Government must all the while look towards a stage when the protocol no longer poisons east-west relations. In the aftermath of any resolution to the impasse, important work will be required to repair relations among the key parties in Belfast and between those parties and the two governments. That will be complicated by unionist fears over the rise of Sinn Féin and the many outstanding points of tension, from language rights to legacy prosecutions, that will remain to be dealt with.
But with Brexit likely to continue to destabilise the UK for the foreseeable future and an erratic London government willing to sacrifice its European relationships for short-term political gain, hopes for any a restoration of pre-2016 east-west relations must be balanced with patient and hard-nosed realism.