Irish unity: What could Mary Lou reply if Britain said ‘take out your cheque book, you can afford it?’

The coincidence is impossible to ignore. Ireland’s €10 billion budget surplus this year is very obviously in the ballpark of Northern Ireland’s £10 billion annual subvention. That is the North’s actual subsidy, not some figure concocted by pretending Britain would pay a united Ireland’s state and public service pensions.

While equating the surplus to the subvention may be simplistic or misleading, this is rarely a bar to the conjectural economics of Irish unity. Sceptics might point out the subvention is recurring, while the surplus could quickly tail off, or disappear. But nothing lasts forever, including the cost of erasing the Border. A paper commissioned by Sinn Féin in 2015 claimed unification could be cost-neutral in about 10 years, implying a one-off bill of €60 billion. The Department of Finance expects the total surplus over the next three years to be €65 billion. A unification fund could be comfortably put together this decade.

Even these back-of-an-envelope calculations are excessive details. The basic political point is much simpler: there is about to be a profound change in how Irish unity is perceived and discussed, at home and abroad. Unionists can no longer cite cost as a compelling objection, not that they could ever do so with pride. Nationalists can advance credible economic arguments instead of retreating to financial fantasy and grievance – failings that have significantly damaged the cause of Scottish independence.

Good fortune appears to have momentarily stunned the Social Democratic and Labour Party and Sinn Féin. Neither party has issued statements on the constitutional implications of the surplus, despite complaining about unprecedented cuts to Stormont’s budget.

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Sinn Féin may be cautious about publicly eyeing up the southern electorate’s windfall. Nor can attitudes change overnight from the poor mouth to a wealthy mindset.

Republicans often say Europe and United States would offer substantial help with the cost of unification. As a more realistic guide, the International Fund for Ireland has raised €1 billion since 1986, three-quarters in its first 20 years, spanning the last decade of the Troubles and the entirety of the peace process up to the St Andrews Agreement.

Today, unification would not be seen by the international community as a post-conflict case for charity. It would be like South Tyrol voting to leave Italy and join Austria. How much aid would Vienna get if it asked for a whip-round?

In a 2020 RTÉ interview, Mary Lou McDonald said, “the British will have to take out their chequebook”, not least because “a section of our people in a united Ireland will consider themselves British”.

The Sinn Féin president has since dropped the reference to Britain having to pay for a united Ireland’s unionist population. The discriminatory idea was presumably unintentional; it would be outrageous to suggest Dublin pays for nationalists’ benefits in Northern Ireland. However, no other argument has replaced it. McDonald now merely repeats that as taoiseach she would expect Britain to pay transitional funding for a united Ireland.

What could she say if Britain replied: “Take out your chequebook, you can afford it?”

That is a question for a possible future. Another possibility is that Northern Ireland starts expecting a slice of the surplus far sooner. The North has its own tradition of putting on the poor mouth, of course, which the peace process has to some extent encouraged and institutionalised. Mandatory powersharing has proved incapable of making difficult decisions, despite the political cover it should provide. As this leads to overstretched budgets and struggling public services, and as London’s financial patience runs out, eyes will naturally turn to the pot of gold across the Border.

When devolution itself fails, as in the present Stormont collapse, nationalist demands for some form of joint authority create a more intriguing call on the Republic’s largesse.

The principle of no taxation without representation cuts both ways. To be meaningful, any enhanced decision-making role for Dublin must have some influence over spending, yet this would involve spending only the UK’s money.

Nationalists might say it is Northern Ireland’s money, raised from their taxes, and Dublin has their mandate to spend it. But the subvention adds a complication. Tax revenues in Northern Ireland cover only three-fifths of public spending, with the remainder raised in Britain. Unionists might say one fifth should come from Britain and one fifth from the Republic for joint decision-making to be legitimate. Some nationalists and others might feel the same.

More pragmatic expectations could focus on the taoiseach’s shared island unit, with its €100 million annual budget, around half of which is spent north of the Border. This budget looks distinctly unambitious beside a surplus 100 times larger, predicted to be 200 times larger by 2026. The A5 dual-carriageway to Derry is an obvious individual project – Dublin promised half its cost at St Andrews, then reneged after the financial crash in 2011.

The time is upon us when being serious about a united Ireland means spending some serious money.