The talks keeps coming back to the delicate patchwork of history, nationalism, religion and geography that intertwine in Northern Ireland
Tensions between Britain and the European Union over their Brexit trade deal exploded into an open war of words on Sunday, with both sides accusing the other of sowing disharmony at the Group of Seven summit.
Ever since the United Kingdom voted to leave the European Union in 2016, the two sides have been trying to solve the riddle of what to do about the British province of Northern Ireland which has a land border with EU member Ireland.
Over years of discussions, they have made little headway, agreeing multiple texts and deals only to find that their solutions fall well short of expectations, and then bickering over what to do.
Ultimately, the talks keeps coming back to the delicate patchwork of history, nationalism, religion and geography that intertwine in Northern Ireland, but the latest spat is centred on sausages.
In a move that some worry could provoke a full scale trade war, Prime Minister Boris Johnson has threatened to unilaterally suspend parts of the Northern Ireland protocol of the Brexit divorce deal.
That protocol essentially kept the province in the EU’s customs union and adhering to many of the single market rules, creating a regulatory border in the Irish Sea between the British province and the rest of the United Kingdom.
But Johnson has unilaterally delayed the implementation of some provisions of the protocol, including checks on chilled meats such as sausages moving from the mainland to Northern Ireland, saying it was causing disruption to some supplies to the province.
During talks with Emmanuel Macron at the G7 summit in southwestern England, Johnson had queried how the French President would react if Toulouse sausages could not be sold in Paris markets.
Britain's Telegraph newspaper reported that Macron responded by inaccurately saying Northern Ireland was not part of the United Kingdom.
"Various EU figures here in Carbis Bay, but frankly for months now and years, have characterized Northern Ireland as somehow a separate country and that is wrong," British foreign minister Dominic Raab fumed.
"It is a failure to understand the facts. We wouldn't talk about Catalonia and Barcelona, or Corsica in France in those ways," he told the BBC's Andrew Marr program.
A French diplomatic source said Macron had been taken aback by Johnson bringing up sausages - which the British leader had said was a crucial issue but the French regarded as a distraction from the main G7 business.
The French president had merely been pointing out the sausage comparison was invalid due to the geographic differences, the source said.
"It took four years to negotiate this deal," the source said. "It cannot be said the United Kingdom didn’t know what it was signing for. It’s either not very professional or a distraction from the real issues."
Despite a U.S.-brokered 1998 peace deal that brought an end to three decades of violence, Northern Ireland remains deeply split along sectarian lines: Many Catholic nationalists aspire to unification with Ireland while Protestant unionists want to stay in the UK.
The EU does not want Northern Ireland to be a backdoor into its single market and neither side wants border checks between the province and the Republic of Ireland which could become a target for dissident militants.
Instead, the two sides agreed checks between the province and the rest of the United Kingdom, though Britain now says these are too cumbersome and divisive. Johnson said on Saturday he would do "whatever it takes" to protect its territorial integrity.
"It is time for the government to stop talking about fixes to the Protocol and get on with taking the necessary steps to remove it," said Edwin Poots, leader of Democratic Unionist Party, Northern Ireland's largest political party.
He said he has written to Macron whose comments he described as offensive and ignorant.