The British government has given its first official hint that it hopes the Irish external border will provide the solution to one of the most vexing conundrums of Brexit: how to pull up the immigration drawbridge without installing a “hard border” of customs posts and passport checks between Northern Ireland and Ireland.

James Brokenshire’s statement that the focus in a post-Brexit world is to “strengthen the external border of the common travel area” is likely to mean that the only physical passport checks an international traveller will face on his or her way into Britain via Ireland will be at an Irish airport or seaport.

Asking the Irish to carry out Britain’s passport checks may not be what Brexiters had in mind when they campaigned to “take back control of Britain’s borders”. Indeed, the chairman of the Vote Leave campaign, the former chancellor Lord Lawson, explicitly called for the return of a hard border between Northern Ireland and the Republic during the referendum campaign.

How will Brexit affect Ireland? Britain's decision to leave the EU affects Ireland in myriad ways. The fall of sterling has hurt Irish exporters, who sell £15bn of products in Britain every year. There is deep uncertainty over what will happen to the border between Ireland and Northern Ireland after Brexit. Few want a return to a 'hard border' studded with checkpoints, yet fully open British frontiers seem destined to disappear. Ireland has opportunities too, not least that it could attract banks, financial firms and other businesses wary of investing in an isolated UK with an uncertain future.



But the development of electronic border systems – essentially passenger databases – by both British and Irish governments over the past decade make it possible to operate a digital “outer common perimeter” around both countries.



Neither system has been without major problems, but the collection of advanced passenger information at the time of booking and the transmission of passenger name records on international flights has now become routine. The data collection will soon be extended to include all flights within the EU.

Those databases enable both governments to screen out those barred from entry before they even get on the plane. They mean that a passenger arriving at Dublin airport could face the same digital checks as any arriving at Heathrow.

As Brokenshire indicates, this process is already under way, with the Irish government recognising UK short-term visitor visas for travel to Ireland for visitors from 16 countries, including India and China. A common short-stay visit visa is also being pursued.

In March, Ireland passed legislation allowing the UK to require airlines and ferry companies to provide advance passenger details on all UK-Irish journeys. The Northern Ireland secretary is making clear this work will accelerate and the existing Operation Gull to tackle illegal migration to Northern Ireland expanded to close any potential backdoor to Britain post-Brexit.



Only a relatively small number of EU citizens would want to come to the UK illegally

As the Irish ambassador to Britain, Dan Mulhall, recently told the House of Lords: “For as long as Ireland is not part of Schengen, everyone coming into Ireland from continental Europe and beyond has to go through passport control at our airports and ports. Therefore, the only people who will have the right of free movement into Ireland and the right to live, work, visit and settle in Ireland will be European Union citizens.



“It is, of course, true that an EU citizen could come to Ireland after Brexit, settle in Ireland and then decide to go across the border to Northern Ireland and then to Britain, but they would be illegal immigrants. As I understand, most Europeans are not interested in being illegal in any European country … It seems to me that only a relatively small number of European Union citizens would want to come to the UK illegally.”

Mulhall said in the “worst-case scenario” that the UK government decided to curb freedom of movement to prevent all other EU citizens living and working in Britain, the Irish border would not pose an additional risk. All EU citizens would presumably still have the right to enter and visit Britain and pass any external passport control, so any future work permit system would likely be enforced with internal checks by employers through a registration, national insurance or identity card system.



Customs checks are a different issue, but academics say they could operate on the same lines as those between Norway and Sweden where mobile spot checks don’t necessarily take place at the physical border.