“And for those who came back home again what changes did they find,

For the counties that made Ulster up they no longer numbered nine.

Three counties had been stole away by those we fought to save,

For now this was England’s gratitude to the sacrifice we made.”

That verse is from a loyalist song called “The Englishman’s Betrayal“.  It tells of how “Englands cry for help” at the start of the First World War was answered by the Ulster Volunteers.  At the Battle of the Somme, “twenty thousand Ulster men they prepared to fight and die”.

The German soldiers who oppose them wonder “what kind of men are these” who “would leave their native land” to fight for others.  The answer is given by what the Ulstermen do rather than what they say. “On the mud and on the wire, they left behind their dead”.

“The only flag to fly that day behind the German lines” is “the old red hand of Ulster with its Shamrocks bound in nine” – advanced there by the 36th (Ulster) Division.  Thence to the Englandman’s Betrayal, as three counties are torn from historic Ulster, and given to others who didn’t volunteer to fight.

We tell the story of this song in some detail because it provides some context for Boris Johnson’s new deal, its provisions for Northern Ireland, the rift with the Democratic Unionist Party – and the hostility to the deal of a large swathe of Unionist opinion in Northern Ireland.

For although it is part of the United Kingdom, many Unionists fear that the latter’s largest component, England, will ultimately sacrifice them for its own convenience.  Sometimes, this fear is sublimal; at other times, rampant.  But it is always there, stowed away in the depths of the Unionist psyche

Hence the formation of the Ulster Volunteers in the first place – formed in 1912 to resist a United Ireland, and defend the Ulster Covenant by (as that document put it, with Dominic Cummings-style starkness) “all means which may be found necessary”.

The Prime Minister’s deal should be seen against the shadow of this long story, and it should be admitted at once that there is something in it.  England tends to regard Northern Ireland as a place apart.  Provisionality has been present in government policy since the creation of the statelet.

Then first the Anglo-Irish Agreement under the Thatcher Government, and then the Belfast Agreement under Tony Blair’s, reinforced Northern Ireland’s uniqueness, by seeking to balance the Unionist tradition with the Nationalist one, and giving the Republic of Ireland an input into its neighbour’s governance.

This is not to say that either development was wrong, nor that the Nationalist case should be treated with anything other than respect – what a mess England made of its Irish policy over the centuries – nor that Unionists always governed Northern Ireland well or justly, nor that Thatcher was mistaken when she said that Northern Ireland is “as British as Finchley”.

But just because it is as British as Finchley doesn’t mean that it can or should be governed in exactly the same way as Finchley – any more than Scotland or Wales should.  Many Unionists agree: these have long wanted devolution, not integration, and duly got it during the 1990s.  Which brings us back to Johnson’s deal.

Look at what it does for the Union, he would say.  The anti-democratic backstop has been scrapped.  The EU and Ireland have been forced to separate customs checks from other ones, which they previously claimed was impracticable.  Democratic safeguards have been inserted.  Above all, Northern Ireland will leave the Customs Union with the rest of the UK.

The DUP would answer that this is all very well, but that. under the terms of the deal, Northern Ireland’s separation from the rest of the country will widen.  Much of it will be in the Single Market; Great Britain will leave it.  It will follow the EU’s customs code; Great Britain won’t.  The safeguards don’t provide enough safety, at least for Unionists.

The party is conflicted (part of ithe coalition that votes for it leans towards the deal) but has formed a consensus view: the deal is one more “Englishman’s betrayal”, delivering them a step closer to a United Ireland.  Its members are especially resentful that Johnson came to their conference, said one thing about borders in the Irish Sea – “no British Conservative government could or should sign up to any such arrangement” – and then did another.

The Conservative Party and the DUP are not sister parties: ultimately, they go their separate ways.  The Tory position is especially complicated by the presence of Conservatives in Northern Ireland, who are not shy of standing against the DUP in elections.

None the less, the Party owes the DUP something – after all, it has been its confidence and suppy partner – and will always have a special relationship with this other Unionist Party.

Our take at ConservativeHome is that, when it comes to the deal, the DUP is more sinned against than sinning.  Were the agreement’s Northern Ireland terms the only ones in the deal we would oppose iit.  But they aren’t and, like the veteran Eurosceptic Martin Howe, we believe that the agreement as a whole, with its prospect od a free trade deal, is acceptable.

But that there is this rift with the DUP, and that the deal pushes Northern Ireland deeper into a constitutional no man’s land, with implications for Scotland and the whole UK, should worry all Unionists deeply.  Even if the upside is that Irish Nationalists are likely, on balance, to approve of much of the deal – which in turn will ease the pressure for a referendum on Irish unity.

The DUP may well be too angry with Johnson at present to talk with him at all.  But that shouldn’t stop the Conservative and, yes, Unionist Party from seeking to balance the deal’s green shift with a red, white and blue one elsewhere – not just in Northern Ireland, but in the Union as a whole.

For there is even more at stake than the former’s future under the Johnson deal.  Since the Blair devolutionary shake-up, the four parts of the United Kingdom have developed higgledy-piggledy: government has not tried to make sense of the mess, and strengthen the Union as a whole.  The SNP are campaigning to weaken and destroy it as we write, and came close in the Scottish referendum on independence.

Which is why Johnson should perhaps soon make Michael Gove, who will be out of a job post-Brexit, the boss of a new deparment – as Secretary of State for the Union.  He would bring his intellectual creativity to firming it up – a project which, as Lord Ashcroft’s new polling confims today, would have a solid reservoir of support in England.

How to square this with a new strategic relationship with Ireland is one of the Johnson Government’s greatest challenges.  ConservativeHome will be looking this week at ways in which the Union might be strengthened, drawing on the work of Policy Exchange.

And the Conservative Party should be putting its thinking cap on – at least if it does not want to provoke new charges of selfishness and betrayal, and risk the future of “our precious Union”:

“So gather round my comrades, this first of July morn

When Ulster men are proudly glad of the land where they were born

And we’ll never more be sent away to fight in a foreign land

Or to die for someone elses’ cause at an Englishmans command.”