Brexit and the Irish border: A simple explanation
The Irish border problem has been a major sticking point for Brexit. Tory leadership contenders Boris Johnson and Jeremy Hunt have been setting out their solutions during a visit to Belfast.
What's the problem?
If Brexit happens, the 310-mile Irish border will represent the only land border between the UK and the EU.
As well as no longer being in the EU, Northern Ireland is likely to end up with different rules and standards to its neighbour, the Republic of Ireland.
That's because the UK intends to leave the customs union and single market - arrangements designed to make trade easier between EU countries.
Lorries travelling to the EU from Northern Ireland would be required to stop at the border for document checks and some product inspections. This would be to ensure their goods meet EU standards.
In theory, such checks would mean things like cameras and security posts, creating a so-called "hard border".
So why hasn't it been sorted yet?
UK and EU Brexit negotiators came up with a solution - known as the Irish backstop - to avoid border checks.
If used, the backstop would keep the UK in a very close relationship with the EU until a trade deal permanently avoiding the need for checks is agreed.
However, the backstop proved unacceptable to many Conservative MPs, who worried the UK would be trapped in it.
Their opposition eventually led to Theresa May's resignation as prime minister.
Boris Johnson and Jeremy Hunt have pledged to go back to the EU to negotiate changes to the backstop. They believe they could do this before the current Brexit deadline of 31 October.
Can technology solve the problem?
A "wealth of solutions" including technology could avoid the need for a hard border after Brexit, insists Boris Johnson.
Jeremy Hunt also says he will fund solutions to deliver his "cast iron guarantee" to avoid a hard border in Ireland. He believes this could be done using existing technology.
Supporters say custom checks could be done at warehouses before lorries set off. Mobile phone technology or microchips on lorries, would track goods and avoid the need for border posts.
However, the EU does not currently share a single border with a non-EU country where checks have been completely eliminated.
That includes Norway (not in the EU) and Sweden (an EU member) - which share one of the most technologically advanced borders in the world. Their main crossing point processes about 1,300 lorries a day, with each waiting 20 minutes on average.
The EU has said it will consider other solutions to the Irish border problem, but only once the current Brexit deal has been signed off. It has also expressed doubts about a technological solution:
"We looked at every border on this Earth, every border the EU has with a third country - there's simply no way you can do away with checks and controls," its director-general for trade, Sabine Weyand, said in January.
The problem with just relying on technology, is that EU law also require some products to be physically checked - chemicals and food are among them.
- Single UK-Irish food zone suggested by report
- Border technology 'could take 10 years'
- Why are vets being recruited in Ireland?
What else could be done?
Alongside technology, Mr Johnson has also talked about a trusted trader scheme. Businesses would be allowed to physical by-pass checks once they've proven to be trustworthy and have met certain standards.
For it to work, the UK would need to persuade the EU to recognise it.
But setting up such a scheme would a take a lot of time and cost a lot money. The UK would also need to come up with an effective way of enforcing it and prevent smuggling.
Achieving all of this by 31 October would be extremely difficult.
Northern Ireland exported almost £3bn of goods to Republic of Ireland in 2017
Trade in £ millions
What happens if there's a no-deal Brexit?
Should the UK leave the EU with no deal on 31 October, then, in theory, checks will be required.
But no one has started building border posts and the UK and Irish governments say they don't want a hard border.
One proposal, in the event of a no-deal Brexit, is to allow physical checks on animals and other goods to take place in "mobile units away from the border".
However, existing EU law states that animal checks must take place at designated Border Inspections Posts (BIPs) "in the immediate vicinity of the point of entry" - which would include the Irish border.
The EU says "geographic constraints" are the only exception (eg mountains, cliffs, valleys, rivers). In these cases, "a certain distance from the point of introduction may be tolerated."
So getting the EU to allow checks to take place away from the border, for non-geographic reasons, would require a change in the rules.