Thread by @BBCDomC

Now. Rather usefully for non-constitutional lawyers, also known as mortals, Lord Pannick is explaining the PM's power. First off, the PM has what's called prerogative power - a power that used to be the monarch's to prorogue Parliament.

Pannick: "Our case is that the PM's advice to Her Majesty to prorogue Parliament for five weeks is an unlawful use of the power. It breaches Parliamentary sovereignty - the effect is to remove the ability of Parliament to enact legislation [as the Brexit deadline looms]"

He adds that closing down Parliament also prevents MPs and Peers from asking ministers potentially vital questions on the government's Brexit strategy. Parliamentarians would be in the dark about what would be going on.

"My point is that a prorogation for five weeks prevents Parliament from addressing these issues as it sees fit during that period."

There is no dispute that the PM is entitled to decide that it is appropriate to end this session of Parliament, [ahead of a Queen's Speech]. "We say that he is not entitled to close Parliament for five weeks at such a critical time without justification."

The abuse of power goes further, says Lord Pannick. The PM's own submissions show he "does not understand the role of Parliament".

The PM does not understand the constitutional functions of Parliament in holding the government to account, he adds. "The advise to Her Majesty [to prorogue Parliament was an abuse of power."

Lord Pannick: "Under our constitutional law, Parliament is supreme. This court has the power and duty to ensure that there is no abuse of powers by the Prime Minister. The court must have jurisdiction to consider these matters."

The PM's legal team says there is no precedent for the courts to intervene.

Pannick: "We say that there is no precedent because no PM in modern history has abused his power" in this way.