Q&A
WHY IS THE BORDER AN ISSUE?
Brussels has said it will not discuss a trade deal until progress is made on three bones of contention – this is one.
What the British and Irish governments say appears incompatible – and the row could impact on the peace process and Mrs May’s minority government.
STATUS OF THE BORDER
It has existed since the 1920s, but has never had full custom checks. During the Troubles there were military checkpoints – but not a restrictive complete border.
COULD BREXIT CHANGE THIS?
The crucial issue is British membership of the customs union and the single market.
All EU countries have to abide by the same rules affecting business. Brexit could change that.
WHAT IS THE BRITISH POSITION?
Theresa May has pledged to take the UK out of both the single market and the customs union. But she insists there must not be a physical border between the north and south of Ireland.
WHAT IS THE IRISH POSITION?
PM Leo Varadkar believes this is not workable – and has threatened to veto trade talks if progress is not made.
He wants a written guarantee that the border between Northern Ireland and the Republic will remain ‘invisible’. Ireland suggests the UK should allow Northern Ireland to carve out its own special status, effectively staying in the customs union and the single market even when the UK leaves.
WHAT DOES THE EU SAY?
Brussels does not want a hard border. But after Brexit, the UK will be free to cut trade deals with other countries.
That could mean importing items currently blocked by the EU. Ireland would therefore have to police the border to ensure this does not happen – indicating some sort of border checks.
WHAT DOES THE DUP SAY?
The most powerful party in Northern Ireland will not agree to staying in the customs union. The pro-Brexit first minister, Arlene Foster, says that could undermine the link with the UK. The ardent Unionist has accused Mr Varadkar of using Brexit to bring a united Ireland closer.
WHY IS HER INTERVENTION VITAL?
The DUP props up Mrs May’s government after she lost her Commons majority in the election – forcing her to sign a confidence and supply agreement with the party. This means the DUP backs the Tories on crucial votes.
WHAT ABOUT PEACE PROCESS?
Some fear the row could harm the peace process by undermining relations between the DUP and Sinn Fein.
The IRA gave up its campaign of violence after the UK agreed to a cross-community government in Northern Ireland.
But now the province’s devolved government, which was shared between the DUP and Sinn Fein, has fallen apart.
Before he died, Sinn Fein’s Martin McGuinness warned that a return to border checks could put the peace process in peril.
WHAT IS THE WAY FORWARD?
Hard to say. Donald Tusk, the president of European Council, has given Mrs May a ten-day deadline to reach a deal over the border. Liam Fox said trade talks could start without a deal – meaning that the tussle could continue for months.