Madrid: All of a sudden, since Britain voted to leave the European Union, there’s been a huge increase in the number of Brits who have discovered their Irish grandparents.

Under Irish law, anyone with a grandparent who was born anywhere on the island of Ireland, or those who live now in Northern Ireland even though it is part of the United Kingdom, qualifies for an Irish passport.

And since Brexit, the number of British citizens now applying for a separate Republic of Ireland passport has doubled.

In 2013, for example, 91,924 people living in the United Kingdom filled out Irish passport application forms. Now, after the June 2016 referendum that saw a majority of Britons support a break from the 28-member EU bloc, nearly double the number of Britons are now seeking Irish passports.

According to a question tabled in the Irish parliament in Dublin, 162,251 people living in the UK filed Irish passport applications.

So far in 2017, up to the beginning of December 81,297 applications came from England, Scotland and Wales, while 80,964 people living in Northern Ireland have applied for Irish passports. In 2015, the full year before the Brexit referendum, just 53,715 people in Northern Ireland applied for a Republic of Ireland passport.

For Britons, having an Irish passport means that they can continue to live, work and travel across the rest of the EU without pre-conditions or visa rules that may apply to UK citizens once it leaves the economic and political bloc at 11:01pm on March 29, 2019.

The surge in applications is coming at a cost to the Department of Foreign Affairs in Dublin. In April alone, it spent €1,872 (Dh8,115) on diplomatic courier services to send completed application from the Irish embassy in London to Dublin for processing. There’s also an online service, and it dealt with more than 11,000 passport applications from Britain between April and August alone. It takes seven weeks for an initial passport application to be dealt with and issued.

Since the Brexit vote, more than 1,000 UK companies have opened registered offices in Ireland, a move that would sidestep some of the negative consequences of leaving the common EU customs and economic zone.

Ireland and the UK are in the same time zone, share a common language and similar legal systems, and both have a common travel area outside of the Schengen visa area that applies to continental Europe.

So far this year, the Irish passport office has processed 752,296 new passports up to the beginning of December, with another 26,000 under processing. Last year, 733,060 passports were issued, and 672,760 were issued in 2015.