There should be no question of a physical border being erected between Northern Ireland and the Republic

It is intolerable to Irish interests that the possibility should have been left hanging by Theresa May and her ministers – it is understandable that Irish Prime Minister Leo Varadkar should demand a written agreement rather than verbal assurances

Who could blame Leo Varadkar for threatening to block trade talks until the issue is resolved? (PA)

It has become fashionable – especially among the harder Brexiteers – to present EU representatives and negotiators as the bogeymen who are holding up Britain’s withdrawal and our glorious future. It is more attractive to blame men like Jean-Claude Juncker and Michel Barnier, who can be portrayed as stooges of a faceless and stateless European bureaucracy, than to hold responsible the elected leaders of specific countries who are representing identifiable national interests.

For this reason, the intervention by the Irish Prime Minister, Leo Varadkar, in the tortuous Brexit negotiations seems like a significant moment. His warning that the Irish government will not tolerate a physical border between Northern Ireland and the Republic cannot be disregarded as simply rhetorical bargaining by Brussels bureaucrats. Rather, Mr Varadkar is the man elected to represent the UK’s nearest neighbour, the head of a nation with which Britain has the closest ties of any in Europe – ties based on close trading links, a shared language and an interwoven history. For all the ups and downs, for a great many people in this country the Irish are family.

As such, Mr Varadkar’s remarks require Britain’s full and immediate engagement. His call for a commitment on the border question to be made before trade talks begin cannot be ignored. Indeed, the simple fact that he feels obliged to have raised the issue as forcefully as he has is indicative of a harsh reality – that it is David Davis et al who have failed to get a proper grip on the key, first phase questions in the Brexit negotiations, not the Barnier camp.

What’s more, the Irish PM is absolutely right that there should be no question of a physical border being erected between Northern Ireland and the Republic. It is plainly intolerable to Irish interests that the possibility should have been left hanging by Theresa May and her ministers – and it is understandable that Mr Varadkar should demand a written agreement, rather than the verbal assurances which have been offered so far. Who could blame him for threatening to block trade talks until the issue is resolved?

It is plain from Mr Varadkar’s choice of words too that there is intense frustration in Dublin over the way in which the Brexit talks are progressing – or not progressing. To accuse pro-Brexit politicians of not having “thought all this through” in the years prior to the referendum will hardly go down well among the architects of Britain’s EU departure.

Yet in truth it can hardly be regarded as a point of great contention. It is all too obvious that the Irish border question is one to which Brexit supporters gave far too little consideration during the referendum campaign and the period before then. Instead, it was simply the subject of assertion and assumption – like most elements of the pro-Leave vision for our future.

Ardent Brexiteers – and horse-trading pragmatists – insist that the Government is right to hang on to any potential bargaining chips in order to force the EU into concessions of its own. Yet this misses the fundamental point that a no-deal outcome will have more impact here than in the EU’s remaining member states. To argue otherwise is to ignore every economic reality and to rely instead on a vague conviction that all will be well.

The renewed focus on the Irish border issue heaps more pressure on Theresa May at the end of (another) bad week. Her decision to fix the Brexit date in law backfired spectacularly and at the EU summit in Gothenburg she has been told in no uncertain terms that the divorce settlement offered to the EU this far is inadequate. Leo Varadkar’s intervention is the bitter icing on a crumbling cake. European council chief Donald Tusk telling the UK that no trade talks without progress on money and Ireland is the cherry.

In the past, “Irish questions” have proved difficult to resolve. That is one of the reasons why it is so important for the UK Government to be clear once and for all – in writing – that there will be no hard border where Northern Ireland meets the Republic. Any other outcome would be disastrous for prosperity and perhaps even peace too.

Leo Varadkar’s words may have sounded hard, but they should be taken as advice from a friend – and acted on with due urgency.