TRIGGERING Article 50 without consulting Edinburgh, Cardiff and Belfast would dissolve the “glue,” which bound the United Kingdom together, the UK Supreme Court heard on the final day on the Brexit case.

Richard Gordon QC, acting for the Welsh government, told the 11 justices: “The importance of the Sewel Convention is not its legal enforceability but that it represents a dialogue between Parliament and the devolved legislatures.”

He said UK Government ministers should not "short circuit" the need for Westminster to consult the devolved administrations when passing certain legislation and stressed the Sewel Convention – which says Westminster will not normally legislate in regard to devolved matters without Holyrood’s consent - was a very important constitutional force in society.

Read more: Constitutional battle now between PM's red, white and blue Brexit and the "Tartan Remain," says Wishart

“The reason why it is such a constitutional force is that it is the glue and the only glue that can really hold an unwritten constitution together,” he argued.

Mr Gordon claimed the "fault line" through the UK Government's argument was that while its executive "prerogative" powers could be used to make and unmake treaties, they could not "dispense with laws passed by Parliament".

He added: "This is elementary; a child of six, with respect, could understand this point."

Mr Gordon’s remarks followed the arguments posited by James Woolfe QC, the Lord Advocate, who insisted that if the judges ruled that there should be a new law to trigger Article 50, then the Sewel Convention should apply; that MSPs should have a vote too given how EU law was intertwined with the devolved settlement in Scotland.

“Fundamentally,” said Mr Woolfe, “I say this case is about who has the power to change the law of the land.

“In Scotland, there are three legislatures: there is the United Kingdom Parliament; there is the European legislature; there is the Scottish Parliament; and as between the United Kingdom Parliament and the Scottish Parliament, the convention constrains the United Kingdom Parliament in the exercise of its legal powers in order to respect the authority which the Scottish Parliament has.”

Read more: Constitutional battle now between PM's red, white and blue Brexit and the "Tartan Remain," says Wishart

Manjit Gill QC, who represented the children of European Economic Area nationals who could be directly affected by Brexit, spoke of a “usurping executive,” and insisted: “This is not time to turn to a flexible constitution. It’s a slippery slope.”

For the UK Government, James Eadie QC, told the court rights related to EU membership were created and taken away "on the international plane" rather than by domestic legislation; so a new act of Parliament was not required for Brexit.

Mr Eadie, who presented his argument to the court on Monday, was responding to the points raised during the hearing and reiterated his argument that Westminster had wanted ministers to have a "prerogative" power to trigger Article 50.

The UK Government lawyer raised Wednesday night's Commons vote on Brexit - where MPs overwhelmingly backed the Government's planned timetable - saying it was significant as the Commons had "indicated its view and has done so clearly".

However, he conceded the vote was not legally binding and if the Government lost the case, it would need to prepare new legislation to be considered by the UK Parliament.

At the completion of four days of detailed legal argument, Lord Neuberger, president of the UK's highest court, announced: "It bears repeating we are not being asked to overturn the result of the EU referendum.

"The ultimate question in this case concerns the process by which that result can lawfully be brought into effect. As we have heard, that question raises important constitutional issues and we will now take time to ensure the many arguments presented to us orally and in writing are given full and proper consideration."

Read more: Constitutional battle now between PM's red, white and blue Brexit and the "Tartan Remain," says Wishart

Lord Neuberger added: "Having said that, we appreciate that this case should be resolved as quickly as possible and we will do our best to achieve that."

The judges are due to give their ruling on whether they agree or not in January.