The least London can do is call out Sinn Fein the way it did the DUP

This dual approach to the landmark peace agreement, fully supported by Dublin, began in June of 2016.

It is obviously legitimate and also unsurprising that nationalists were annoyed at the UK decision to leave the EU. But this led to bogus claims about the agreement having depended on EU membership or having guaranteed an open border.

It did no such thing. There is a much more plausible case to be made that it was a breach of the spirit of the deal, which was agreed at a time when no-one envisaged either party leaving the EU, but that is a different argument.

Dermot Nesbitt, on the opposite page (see link below), accuses the British and Irish governments of having failed to hold Sinn Fein to account for its failure to recognise the legitimacy of Northern Ireland, which was at the core of the agreement and the consent principle.

Mr Nesbitt’s comments are all the more significant given that he was on the moderate wing of unionism, and he helped the Ulster Unionist Party during their negotiations towards it.

As Mr Nesbitt says, the failure of the two governments is all the greater given that they singled out the DUP for criticism recently, something they have never shown any inclination of doing to Sinn Fein, which collapsed power-sharing.

The temptation to accede to all Sinn Fein’s demands and restore Stormont on that basis is, naturally, great, for all other parties, yet it will only be a short-term fix if so.

If the party not only fails to recognise Northern Ireland in its rhetoric, but follows a de-stabilising course of politics in apparent pursuit of that refusal, then at the very least there is a duty on the UK government to call it out.

We know that the Irish government simply will not do this. In fact, Dublin ultimately seems to share or adopt SF demands.

But for London to stay mute is a grave dereliction of its responsibilities.

• Demot Nesbitt: Shame on the two governments