As the Cabinet reconvenes in Chequers after the summer recess, the preparations for Brexit are top of the agenda. Yet amongst all the various options being considered by government ministers, there is one critical aspect of Britain's disengagement from the European Union which has barely figured at all in the official debate - the impact on Northern Ireland and the Irish Republic.

Such an omission is a symptom of the parochial insularity characterising the Tory right's drive for Brexit, and is of a piece with Westminster's historically disdainful attitude towards Ireland.

A history of after-thoughts

The political historians Alistair B. Cooke and John Vincent once wrote in their study of the Home Rule crisis of the 1880s that the "Irish policies of British governments at Westminster cannot be explained in terms of Irish circumstances. They must be explained in terms of parliamentary combinations."

In other words, domestic British politics trumps whatever impact Westminster policy may have across the Irish Sea. This was true of their immediate subject, and it was an analysis confirmed for the subsequent 1910-1914 Home Rule crisis in a more recent study, Ronan Fanning's Fatal Path.

As summed up by one reviewer, Fanning established that for Asquith and Lloyd George "the essential issue…was never Ireland but was, rather, their own party advantage and, above all, their personal career advantage. Both had to spend more time calculating the consequences of their policies for internal British politics, and their own positions, than for Anglo-Irish relations."

The same indictment applies to the Tories who, by instrumentalising Ulster Protestant resistance to Home Rule (playing "the Orange Card" in the infamous words of Lord Randolph Churchill), brought Ireland to the brink of civil war in order to destroy their Liberal rivals.

These events have been prominent in the public consciousness in Ireland during the "decade of centenaries" and in this year especially, one hundred years after the Easter Rising.

Though the stakes are not of the same magnitude, now too can the Tory Party be accused of treating Ireland as an after-thought. The gamble of a European referendum that showed scant regard for the consequences of exit for decades of careful conflict resolution.

The 56 per centers

The new Prime Minister, Theresa May, treads a treacherous, though hopefully not fatal, path as she deals with the fall-out of the European referendum for Northern Ireland and the Irish Republic.

During the referendum, the then Secretary of State, Theresa Villiers, took a Leave position, even as the Irish government and most of the North's political parties warned it would be disastrous. Her position was unsustainable after 56 per cent of Northern Ireland and a clear majority of its parliamentary constituencies voted for Remain, and she has been replaced by the pro-Remain May ally James Brokenshire.

Brokenshire now has the unenvious task of raising Northern Ireland's situation in a heated Cabinet argument about Brexit, the terms of which have been framed with little or no reference to the situation across the Irish Sea.

May and Brokenshire's current bind is this. Though keeping conspicuously quiet throughout the referendum campaign, May has been keen to shore up her right flank by disavowing any notion that the decision to leave the EU would be undone on the sly: "Brexit," she has repeated, "means Brexit."

One on level this is meaningless, since in any referendum with a binary choice it is nigh-impossible to identify the individual motivations of the millions who voted for one or other side.

Yet it is simply inescapable that the mood music of the referendum was the desire to limit immigration from the EU into the United Kingdom.

The Human Rights Act tripwire

It is this commitment, at the very least, that the Tory right in the Cabinet expects to be upheld. Though May was quick to reassure Stormont that "nobody wants to return to the borders of the past", what this means in practice is far from clear.

Fears that May will opt for a form of Brexit-lite, in the form of remaining in the European Economic Area (EEA) - implying some sort of freedom of movement - has had the right wing playing hardball over the summer.

A particularly reckless example of this was Liam Fox's call in late July for the UK to leave the European customs union in order to seek bilateral trade deals with individual states. The Irish Minister for Foreign Affairs and Trade, Charles Flanagan, expressed himself to be "very surprised" at the comments, and Fox was promptly shot down by Downing Street.

A pattern of narrow British insensitivity is forming. Arguably more serious again are the recent comments by Liz Truss, May's Justice Secretary, who has reconfirmed support for the Tory's election manifesto commitment to replace the Human Rights Act with a British Bill of Rights.

The Human Rights Act 1998 incorporated the European Convention of Human Rights (ECHR) into UK law and, if the intention with a British Bill of Rights is to leave the ECHR, it could have grave implications for the whole Northern Ireland settlement.

Though the principle of consent underpinning any changes to Northern Ireland's constitutional position applies only to the option of a united Ireland, the general spirit of consent and bilateralism could be violated by England and Wales's unilateral action.

More to the point, the Good Friday Agreement presupposes joint EU membership and adherence to the ECHR. As Ian McBride has recently written: "During the 1990s the EU provided a stage on which Irish and British politicians met as equals. The wider context of European integration also took much of the heat out of the border issue. It made the idea of a region whose inhabitants had the right to be 'Irish, British, or both' easier to imagine."

The ECHR does not just have a symbolic presence in the peace process, but provides practical safeguards designed to ensure there can be no return to the majoritarian Unionist domination of the past.

The arrogance of Brexit

Whatever its faults, the Agreement governs relations in a region of the United Kingdom and should be treated seriously in the discussions around Brexit. Moreover, it is a bilateral treaty with the Irish government, lodged after its ratification with the United Nations.

That such a settlement could be so casually jeopardised in a fit of sour isolationism and post-imperial arrogance demonstrates once more the British Government's disregard for its international obligations. It is particularly galling in the Irish case that Britain's involvement and obligations were unwanted and unasked for in the first place by a majority of the island's inhabitants.

It should give Unionists pause for thought that Northern Ireland, once more, is only an incidental detail in a Westminster power-play.

Perhaps this crisis will, in James Connolly's words "throw the Irish people back upon their own resources" and provoke discussion of an internal solution to the Irish question.

An optimistic prognosis now, perhaps. Yet, as the Brexit wagon trundles ever onwards, it is a conversation that will become increasingly necessary.