Video report by ITV News National Editor Allegra Stratton

Today's Supreme Court ruling against Boris Johnson’s parliamentary prorogation is the first time the advice of a prime minister to a monarch has been deemed unlawful.

The court ruled under the guidance of the 1689 Bill of Rights – otherwise known as the constitution for the UK.

However, by overruling Boris Johnson’s advice to the Queen, it’s created a dynamic shift for the monarch, the courts, parliament and the prime minister – something that will echo through the course of future UK politics.

The ruling has created a shift in dynamic for the monarch, the courts, parliament and the prime minister. Credit: PA

Kate Williams, a Royal Historian, says it could take the monarch’s powers into unchartered territories.

“It’s a huge moment in British constitutional history, a huge moment in British history, and very significant, not just for parliament, but also for the Queen,” she said.

Any future monarch can exercise their discretion to make their own judgement, despite the advice of the PM. Credit: PA

Whilst a monarch is supposedly to stay unbiased and out of politics, Ms Williams says Mr Johnson’s actions have seen that any future monarch can exercise their discretion to make their own judgement, despite the advice of the PM.

“The monarch does not have to follow what the prime minister advises if the monarch thinks that advice is illegal or incorrect, or not reflective of parliament should be there doing,” she said.

“[Boris Johnson’s] undermined the entire principle of prime minister and the constitutional monarchy.”

Has Boris Johnson undermined his own position? Credit: PA

Professor Meg Russell, from the University of London, says the court’s ruling proves parliament prevails over prime minister, not the court, also agreeing it's undermined Mr Johnson as PM.

“All the judges are doing is saying parliament is the correct place to be making decisions,” she said.

“Parliament is the sovereign body in our constitution, so bring it back and let it take the decisions.

“They’re not trying to usurp parliament’s role, they’re just trying to stop the executive preventing parliament doing its job.”

Gina Miller speaks to the media outside the Supreme Court in London. Credit: PA

Barrister Dinah Rose QC says it demonstrates the UK constitution actually works.

“I do think that this is an example of the checks and balances of the constitution working as they should do,” she said.

Despite concerns the Supreme Court has been dragged through the Brexit battleground and used as a political pawn, she doesn’t believe that is the case.

“The court has been very careful to stress that it isn’t expressing any view on Brexit,” she said.

“What it’s done is simply rule on the case before it. On the question whether government action was lawful.”

“That’s not a political question. It’s a legal question.”