Thread by @BBCDomC

Welcome back! The final session of the case against Boris Johnson closing down Parliament is starting at the Supreme Court. Lord Keen, the government's top law man in Scotland, begins his reply to the week's legal argument.

Lord Keen says that the entire case against the government is, quite simply, wrong because prorogation of Parliament is a political rather than legal issue.

Lord Keen: "What this court is being invited to do is control the length of the prorogation of Parliament... The length of each session of Parliament and their frequency are regulated by constitutional convention - not the law."

Lord Keen: Parliament may, in anticipation of prorogation, move a motion of no confidence in the government.
But, he argues, that the opposition chose not to use such tools. "If they choose not to deploy those tools, it is a political matter - it is entirely for them."

And he tells the court in telly-friendly terms the PM's opponents are inviting the justices into a “political mindfield” .. “[They] are inviting the court into forbidden territory that the courts are not properly equipped to deal with. "

Lord Davd Pannick QC, for Gina Miller, will start his reply to Keen in 12 minutes. He looks entirely unperturbed - and fantastically relaxed - by the attack on his and Aidan O’Neill’s arguments to the Supreme Court.

Update on the government’s document on what-happens-next that we were earlier told we could not have. Lawyers in court providing copies to the media in accordance wth established rules on #openjustice. No idea if it is being published on gov.uk yet.

On that matter, Lord Keen is now turnng to the question of relief. Government maintains that all the court can do is make a declaration that the PM’s advise was unlawful. He’s now arguing with the justices over how far they could go in directing the PM, were he to lose.

Keen, pressed on what the PM would do if he loses, concludes with: "It is not for the Executive to give undertakings to the court [ahead of knowing what it’s ruling is.”

Ok. Last Leg. Lord Pannick QC, for Gina Miller - wrapping up. He's got a 30-minute window to close down all the government's arguments. Gina Miller behind his right shoulder:

Pannick: PM’s view that September sittings of Parliament are a "rigmarole" shows his "failure to understand that Parliament as the sovereign body" will wish to ask questions of the executive, to debate, and it will wish to do so as the [Brexit] negotiations continue.

Pannick: "This prorogation has prevented Parliament from carrying out its scrutiny of the executive at a time when the constitutional principle of the executive being answerable to Parliament is of vital importance."

He then turns to his other line of attack. If the court does not feel that it can find the PM had some “malign” intention, prorogation could still be found to be unlawful by looking at its effect and impact (paraphrased)

(I’m betting this is a crucial matter for the justices)

"The executive, the junior partner, cannot claim some unfettered power to close down the senior partner.”

Lord Pannick says that the government has no case when it claims the court cannot turn to any kind of legal measure or standard to assess whether prorogation was unlawful (1/3)

"It applies the relevant legal principle - the supremacy of Parliament - to the circumstances of the case... The length of the prorogation, the reasons given, the adverse effect on Parliamentary scrutiny…” (2/3)

"And having done that, the court asks itself in light of all those circumstances [and giving Mr Johnson some benefit of the doubt] whether the PM's decision is beyond the scope of his powers. This is standard business in judicial review.” (3/3)

Lord Pannick: “The remedy we seek is that the PM’s advice to Her Majesty was unlawful. We respectfully ask the court to make such a declaration as soon as possible becuase time is of the essence."

He asks the court to ensure that its judgement ensures that Parliament can sit NEXT WEEK.

Pannick: The appropriate way forward is to let Parliament sort out the problem - but it can only do so if the Court first grants a declaration that the advice was unlawful.

Lord Pannick is trying to insulate the judges from a “poliical" decison. He argues that a simple LEGAL declaration of unlawfulness would be enough for the Speakers of the Commons and Lords to know what to do next POLITICALLY. It keeps the judges out of politics.

Lord Kerr asks if the Prime MInister would actually have to do anything at all?

Lord Pannick says he would not.

Lady Hale: Make the assumption that we will produce an answer "as soon as we humanly can"

Lady Hale, president of the Supreme Court, sums up the tension of three days of potentially historic debate:

“None of this is easy."

Lady Hale: “I must repeat this case is not about when and what terms the UK leaves the EU. We are solely concerned with the lawfulness [of prorogation].

LADY HALE SAYS THEY HOPE TO RULE EARLY NEXT WEEK.

And that, finally, is absolutely it. Until we’re back next week*

*Terms and conditions may apply.