BBC Radio 4

Still on the Boris Johnson row, James Robbins, BBC diplomatic correspondent, says that Britain for decades had put its weight behind an enormous, multi-billion pound trading relationship with Saudi Arabia, which was also seen as a vital source of intelligence. Ultimately the UK believed its interests lay with Saudi Arabia. 

He said Mr Johnson had been talking about a whole series of proxy wars which had pitted Saudi Arabia in particular - as the superpower of the Sunni world - against Iran, the superpower of the Shia world - which were being played out in Yemen, and previously in Lebanon and Iraq, as well as now, to some extent, Syria.

"Boris Johnson thought he was speaking a truth that is normally left unsaid and that is what has caused the huge problem," James Robbins told BBC Radio 4's World at One. 

Back to Boris Johnson's recorded comments about Saudi Arabia - BBC political editor Laura Kuenssberg told BBC Radio 4's World at One that, in a different era, political journalists might have expected a resignation or sacking by the end of the day.

But she says the cabinet tradition of "collective responsibility" - where cabinet ministers publicly support the government's decisions - had been "pretty smashed up" by the EU referendum and may have undergone a permanent change.

In Downing Street's response, the prime minister has shown she is willing to slap down Mr Johnson if she feels it is needed, Laura said.

But she said it was unclear whether there would be any further action against Mr Johnson.

Manjit Gill QC, who is representing interested parties and children in the Supreme Court case, says Brexit will mean European Economic Area nationals - EU plus Iceland, Liechtenstein and Norway - being told: "Be ready to pack your bags and go on that day - it's that stark."

He accuses the government of planning to use the Royal prerogative to trigger Article 50 "without there being any prior safeguarding of the rights that would otherwise fall on the day of withdrawal".

"Children are entitled to know what is going to be their position," he says. "Their parents are entitled to know what long term arrangements are going to be made for them."

The court is adjourned until 14:00 GMT

Winding up her submissions, Helen Mountfield QC says the People's Challenge seeks to uphold the divisional court's judgement "because of its importance in a democratic society" that's based on the separation of powers and the rule of law.  

Helen Mountfield QC, who is representing Graham Pigney and others, says she has undertaken an "historical inquiry" into the use of the Royal prerogative.

She argues that it is "perhaps unsurprising" that when modern judges have considered leaving the EU they have simply assumed that any decision would be one for Parliament.

She says her clients and those who consider their EU citizenship "a fundamental part of their identities" believe that if they are to be deprived of it, their elected representatives in Parliament should be responsible for that.

Helen Mountfield QC - the first female to take centre stage this week - who is representing Graham Pigney and others, says "the only dispute is to the extent of the prerogative that exists".

She argues "there is no prerogative power to dispense or change" the law.

Richard Gordon QC concludes his remarks with a joke that he is going to "devolve" 10 minutes of his allocation to Helen Mountfield QC.

Ms Mountfield is representing claimants of the People's Challenge - a crowdfunded initiative, comprising of those living in the UK, Britons resident on the continent and citizens of Gibraltar.

Richard Gordon QC, for the Welsh government, is referring to the Sewel Convention, which applies when the UK parliament legislates on a matter which is normally dealt with by the Scottish Parliament as part of its work.

He argues that if the Royal prerogative is "used to short circuit" the dialogue between two legislatures "it's to ignore the modern dynamic devolution development".

He says the Welsh government is asking the Supreme Court to evaluate "on whether the prerogative in this case can be used to drive through constitutional change of a seismic nature".

Richard Gordon QC, for the Welsh government, says that if as a matter of statutory interpretation the government is right, "important changes of law can be done by a simple signing of paper" under the Royal prerogative.

"We say that misses the point," he says.

He argues that the Royal prerogative "may have effects on law, but what it can't do is dispense with the law itself".

Carole Walker
Political correspondent

Breaking away from the Supreme Court for a moment, Downing Street has reacted to Boris Johnson's comments about Saudi Arabia, which we've been reporting.

The prime minister's spokeswoman has said the comments from the foreign secretary accusing Saudi Arabia of pursuing proxy wars are not the position of the government. The spokeswoman said that Theresa May wants to strengthen the relationship with Saudi Arabia. The spokeswoman said: "We are supporting the Saudi led coalition in support of the legitimite government in Yemen against Houthi rebels."

She said "those are the prime minister's views - the foreign secretary's views are not the Government's position on, for example, Saudi Arabia and its role in the region". 

She said the foreign secretary will be in the region this weekend and it will be an opportunity for him to set out the Government's position on relations with Saudi Arabia and others in the region. 

Asked whether the PM had full confidence in Mr Johnson as Foreign Secretary, the spokeswoman said "yes". 

Richard Gordon QC, for the Welsh government, insists: "We have absolutely no quarrel with the [EU referendum] vote." 

But he adds: "It's almost the most divisive political event that's happened over the last several decades."

He argues that the European Union Referendum Act 2015 has "absolutely nothing to do with the legal issues in this case".

"It's a statute that has died and has fulfilled its purpose," he says, commenting: "You cannot revive a corpse and give it a separate purpose."

He says there is "nothing in the 2015 act that can say anything sensible about the prerogative".

Richard Gordon QC, for the Welsh government, says the use of the prerogative "will dispense with laws".

"If we're right about that we win and the government loses," he says. 

He questions the real meaning of the European Communities Act 1972,  which legislated for the accession of the UK to the Common Market.

"We are still looking at a situation in which prerogative power is being sought to be used to drive through the most major constitutional change in our system at least since 1972," he says.

He argues that the prerogative measure against the trajectory of devolution "doesn't match".

Richard Gordon QC, who represents the Welsh government, opens his submissions by saying Wales is not trying to stop or stall Brexit, but is speaking out because there are constitutional issues at stake that "go far beyond Brexit".

He says "a child of six" would understand one of his points on the power of the Royal perogative.

He claims that if you tell a child it can't go out to play in the garden but it can play in the house, it has no power to play in the garden.

Returning to the matter in hand, he says to accept there is a treaty making power does not mean there's a power to dispense laws or to crucify human rights.

Dominic Casciani
Home Affairs Correspondent

The final day of the historic Supreme Court Brexit hearing kicked off with nobody mentioning the political elephant that’s plonked its large behind in the middle of Court One: the  Commons Brexit vote, backing the government’s proposed Article 50 timetable. 

So why is that? Are the justices and lawyers pretending it didn’t happen? 

Not at all. 

The vote had political importance but, as far as the rule of law goes, it has no weight. 

The Supreme Court must decide what the law requires the government or parliament to do - rather than what it is politically expected to do.

And that means its sole task, irrespective of what happened yesterday in the Commons, is to decide whether Article 50 needs to be triggered by full-blooded legislation. That means a proper Act of Parliament rather than, as Nick Robinson said on the Today programme this morning, an opinion poll of MPs. 

Lord Wolffe, who is the Lord Advocate, concludes his submissions by saying: "Ultimately, what's required here is an Act of Parliament to make a decision on Article 50."

He says it is "not a matter of footnoting" to note that the power to change the laws of Scotland were given to the Scottish parliament.

He says this "sets bounds to the use of the perogative and precludes the UK government" making significant changes to the laws of the land.

Lord Wolffe says the Supreme Court case "is about who has the power to change the law of the land".

He says Scotland has three legislatures - the UK Parliament, the European Parliament and the Scottish parliament.

He says convention constrains the UK parliament "in the exercise of its legal powers in order to respect the authority the Scottish parliament has".

Lord Wolffe, Scotland's chief legal officer who is representing the Scottish government, is the first to speak on the final day of the Supreme Court hearing into whether the government has the power to trigger the UK's departure from the EU - or whether it must get approval from Parliament before doing so. 

Today Programme
BBC Radio 4

Labour MP Ben Bradshaw says he "doesn't have confidence" the Brexit plan "will amount to very much" as major issues like the single market are still "undecided". 

He thinks key European elections, such as in Germany and France, will change the dynamic of negotiations.