I am one of the half-million or so Irish currently living in the United Kingdom. When I took up residence some months ago I immediately registered to vote, and foremost in my mind was the June referendum on UK membership of the European Union. The outcome of that referendum matters greatly to Ireland, for few other EU member states are linked as intimately and in so many complex ways as we are to the United Kingdom.

On her historic state visit to Ireland in 2011, Queen Elizabeth remarked on “the ties between our people, the shared values, and the economic, business and cultural links that make us so much more than just neighbours, that make us firm friends and equal partners”. The reference to firm friends and equal partners is telling, because, as she diplomatically yet pointedly observed: “Of course, the relationship has not always been straightforward; nor has the record over the centuries been entirely benign.”

Today, the political relationships, solidarity and friendships that have grown between us since we joined the European Union on the same day in 1973 have proved pivotal in building the peace in Northern Ireland and the good-neighbourliness between the United Kingdom and Ireland.

The once fraught constitutional ­conflict concerning Northern Ireland is now governed by the terms of the Good Friday Agreement of 1998. Travel the road between Dublin and Belfast today and although one transits from a euro to a sterling zone, and from Ireland to the United Kingdom, there are no border controls, no visible customs barriers, and thankfully no security posts – just an open road both ways.

When Brexit advocates tell me that if the United Kingdom leaves the EU, the open road will remain open, I know they cannot guarantee that. Under Brexit, the border between Ireland and Northern Ireland would become the sole land border and a crucial frontier post between the United Kingdom and the European Union.

In addition to the half-million Irish-born people living in Great Britain, there are 300,000 British-born people living in Ireland. The Treaty of Rome guarantees their freedom of movement. No one can say for certain what rules would apply to the movement of peoples between our two islands after a Brexit.

Bilateral trade between Ireland and the UK is worth over €1bn every single week. Thirty per cent of imports into Ireland come from the UK. We are the biggest single purchasers of British food and soft drinks and the second-largest purchasers of British fashion and footwear. The vast bulk of our energy requirements is purchased from the UK.

It is simply not possible to predict what model or models of trade relationships would emerge after a Brexit, so when the Brexiters tell me that all those jobs and contracts are perfectly safe, I know it is a prediction they are not in a position to make.

Is the European Union perfect? Not at all. Is it better than anything previously devised to secure peace, partnership and prosperity? It most assuredly is. Has it structures ­ordered to its own reform and development? Yes, it has. It has 28 guiding hands, among them the powerful and influential hand of the United Kingdom.

The first half of the 20th century in Europe was littered with the bodies of the millions who died because of the pull of militant politics. The second half was redeemed by the political imagination that grew the idea of a Europe of nations working with one another and not against one another. We are still in the opening chapters of the greatest adventure in collaborative democracy in world history. We have absorbed 28 member states in a relatively short period of time, each very distinctive, each determined to lose none of its essence and identity around the Union table, but each prepared to exercise (not compromise) its sovereignty in a way that prepares a decent future for all of Europe’s children.

The UK is an important pillar of that future. It has strong views on Europe now and on what it could become. It has an experienced and persuasive voice, powerful enough to make a visible impact on the shape and trajectory of the Union in the century ahead. The Brexit alternative is for the UK to sit alone on the sidelines, in a capricious world, trying to construct a riotous host of essential new trade and political relationships while every one of its neighbours moves on – in that same capricious world, but within the established framework of the EU, thrashing out the issues that allow us to follow through on the visionary purpose of securing peace and prosperity through partnership.

Fundamentally, Brexiters are asking the voters to take a monumental gamble. They have failed to persuade me. I will be voting Remain to ensure the continuation of the contemporary, successful relationship between Ireland and the United Kingdom.

Mary McAleese was president of Ireland from 1997 to 2011