Nick Hargrave is a former Downing Street special adviser, where he worked under both David Cameron and Theresa May. He now works at Portland, the communications consultancy.

Throughout Northern Ireland’s ninety-seven year history, the Conservative and Unionist Party has grappled with a dilemma. We are the proud party of the union; committed to its endurance. But we also recognise the unique events leading to Northern Ireland’s creation in 1921. As a number of factors come into confluence in the next few years – and the debate about a border poll in my view inevitably becomes more pronounced – we must tread carefully in how we talk about Northern Ireland. We must continue to recognise the profound weight of history.

Northern Ireland came into being because the Unionist majority who lived there passionately identified with Great Britain rather than Ireland as the latter gained effective independence. These divisions were primarily entrenched by confessional divides but also the superior economic power of the former; many feared for their safety and livelihoods in the Irish Free State. Equally though, there are few Conservatives interested in the subject nowadays who would seriously argue that British conduct towards Ireland in the preceding years was something we can be proud of.

This is the knot which has underpinned Conservative attitudes to Northern Ireland in the century that has passed. We defend its rightful place in the United Kingdom but we recognise the unique circumstances of the past. This attitude was displayed at important milestones such as the Anglo-Irish Agreement of 1985, the Downing Street Declaration of 1993 and the Belfast Agreement of 1998.

The Belfast Agreement was a landmark event that put Northern Ireland on the path to a better, peaceful future. But we must always remind ourselves that it did not lead to the end of history.

Its contents are premised on a clear declaration of intent that Northern Ireland’s place in the United Kingdom is not in question until at “any time it appears likely to him [the Secretary of State for Northern Ireland] that a majority of those voting would express a wish that Northern Ireland should cease to be part of the United Kingdom and form part of a united Ireland”. At which point a border poll will be called – and if a majority votes for a united Ireland then the UK Parliament would give effect to this outcome.

It is my view that events in the next ten to twenty years are likely to put this hypothetical situation to the test.

The next census of Northern Ireland is due in 2021. Its predecessors have shown a steady uptick in the number of people who identify as Roman Catholic; from 28 per cent in 1981 to 45.1 per cent in 2011. 2021 could well see a further rise. Do not misunderstand me: being a Catholic does not automatically make you in favour of a united Ireland. It is this sectarian blend with nationalism that caused so much historic pain. But we are foolish to believe that new statistics will not lead to new calls from some at the more forceful end of the debate.

There are other potent structural circumstances too. Ireland has in recent years moved from a restrictive semi-theocratic state to a more relaxed definition of Irishness; the psychological barriers of the past may be less pronounced for some. The economic gulf between the United Kingdom and Ireland of the mid-20th Century is no longer so apparent. For Northern Ireland’s youngest children the despicable terrorism of the Provisional IRA is – mercifully – history rather than memory. And of course there is Brexit: cross border status is less important when Britain and Ireland are both in the EU.

All this helps explain why in a recent survey for the BBC in June, 45 per cent of people in Northern Ireland expressed a wish to remain in part of the UK, and 42.1 per cent said they would like to join Ireland. There are other issues to consider in this dynamic, not least opinion in the Republic which is far from open and shut, but the trajectory to a renewed debate is clear.

As the Belfast Agreement states, reunification is an issue for the people of Northern Ireland to decide. But should this test come, Conservatives should have one overriding objective: to preserve peace. Peace at all costs even if the hardest peripheries of the unionist and nationalist communities take a different view.

The objective is uncontroversial. But the strategy will involve the Conservative & Unionist Party grappling with some difficult questions.

First, we must think carefully in future parliaments about Westminster pacts with any party in Northern Ireland. We cannot be in a situation in ten years’ time where we are in government, support for a border poll is demonstrably higher than now – but we cannot take a view because of our parliamentary situation.

Second, should any referendum be held, we must be measured in our involvement. During a referendum campaign, caricatured views and the trading of adversarial language can become commonplace. We do not have to be neutral. It will always be our preference as a party that Northern Ireland remains part of the United Kingdom. But it is not sensible for our relations with Ireland, or with the nationalist community, for our party to be vigorous campaigners, as seen in the Scottish referendum.  This referendum would be about Northern Ireland joining another country rather than independence: it is different. Our overriding concern would be to ensure that the referendum was conducted responsibly.

Third, we need to reflect on how we talk about Scotland’s place in the Union and how that relates to Northern Ireland. If we don’t talk about it then we should not be surprised if a border poll leads to justification for another Scottish referendum. But clearly it is imperative to talk about it sensitively and intelligently.  I think the key point is that our union has equal integrity but not equal history. Scotland was joined in union with England and Wales in 1707 at the agreement of both parliaments, if not all the people. Northern Ireland is a product of a separate historical process in the nineteenth century and early twentieth enturies, which all but the most blinkered Conservatives would now agree did not reflect well on the glory of our country. It was uniquely designed to protect the rights of those who wished to identify as British at a time when the alternative could have been existential. Northern Ireland is therefore profoundly unique.

There will be those who say this is for the future; do not engage now. If the history of Northern Ireland has shown anything though, it is that sound decisions are rarely taken once events are at the height of passionate intensity. It may not be a salient electoral issue. Even at the height of the Troubles, Northern Ireland rarely was. But some things are more important than that. The Conservative & Unionist Party could afford to spend a little time planning ahead.