Pressure is piling on Theresa May not to agree a special case deal for Northern Ireland, after yesterday's much-hoped for breakthrough was scuppered by the DUP.
A deal had been signed up to by Dublin and London, and was being briefed out in Brussels, with parties on both sides visibly relieved that the Brexit impasse had been broken with an agreement that there would be "regulatory alignment" on the island of Ireland, avoiding the need for a physical border.
But it was not to be.
After a last-minute phone call with DUP leader Arlene Foster, May had to concede she could not strike the deal with Jean-Claude Juncker. A brief, and much-delayed, press conference yesterday afternoon concluded that there would be no deal, and a subsequent press conference with Taoiseach Leo Varadkar revealing just how close to an agreement they had come.
As well as upsetting the DUP, the proposal ruffled the feathers of SNP leader Nicola Sturgeon, Welsh first minister Carwyn Jones and London Mayor Sadiq Khan, who argued that Northern Ireland should not get special treatment.
This morning Scottish Conservative leader Ruth Davidson added her voice to the many regional leaders who said that if the Prime Minister is considering regulatory alignment then it should be applied to the United Kingdom as a whole.
Davidson said: "“The question on the Brexit ballot paper asked voters whether the UK should stay or leave the European Union – it did not ask if the country should be divided by different deals for different home nations.
“While I recognise the complexity of the current negotiations, no government of the Conservative and Unionist Party should countenance any deal that compromises the political, economic or constitutional integrity of the United Kingdom.
“All sides agree there should be no return to the borders of the past between Northern Ireland and the Republic of Ireland.
“Similarly, jeopardising the UK’s own internal market is in no-one’s interest.
“If regulatory alignment in a number of specific areas is the requirement for a frictionless border, then the Prime Minister should conclude this must be on a UK-wide basis.”
Yesterday, the Prime Minister's spokesman insisted that the territorial and economic integrity of the UK would be "protected" after Brexit.