In this image taken from video made available by the Supreme Court in London on Tuesday Sept. 24, 2019, senior judge Brenda Hale reads a ruling. In a setback for Prime Minister Boris Johnson, Britain's Supreme Court has ruled that the suspension of Parliament was illegal. The ruling Tuesday is a major blow to the prime minister who had suspended Parliament for five weeks, claiming it was a routine closure. (Supreme Court via AP)

What a way to mark your 10th anniversary.

A decade almost to the day after its creation, the U.K.'s Supreme Court stamped its authority — unanimously and unequivocally — on British politics with a thundering repudiation Tuesday of British Prime Minister Boris Johnson's decision to suspend Parliament.

The court's president, Baroness Hale of Richmond — Brenda Hale to her friends — breezily embraced her moment in the constitutional spotlight, speaking in measured tones in a 15-minute speech broadcast live across the nation as she read the landmark ruling from the 11-judge panel.

Hale slammed Johnson's decision to ask Queen Elizabeth II, Britain's head of state, to suspend, or prorogue, Parliament, sending lawmakers home for five weeks as the clock ticks down to the country's Oct. 31 deadline to leave the European Union.

"Parliament, and in particular the House of Commons as the elected representatives of the people, has a right to a voice in how that change comes about," Hale said. "The effect (of suspending Parliament) upon the fundamentals of our democracy was extreme."

Lawyers for the government had argued that the case was a political, not a legal, issue and that Hale and her fellow judges did not have the right to rule on the case. Hale rejected that, saying that British courts "have exercised a supervisory jurisdiction over the lawfulness of acts of the Government for centuries."

"The decision to advise Her Majesty to prorogue Parliament was unlawful because it had the effect of frustrating or preventing the ability of Parliament to carry out its constitutional functions without reasonable justification," Hale said.

The daughter of two school head teachers from the northern county of Yorkshire, Hale was the first woman justice at the top court and was elected its first female president in 2017.

Tuesday's ruling was a defining moment for the Supreme Court, which was formally established on Oct. 1, 2009, to replace the Appellate Committee of the House of Lords as the highest court in the U.K. That brief history is in marked contrast to the U.S. Supreme Court, which dates back to 1790.

The change in 2009 resulted in the court's judges, known in Britain as justices, becoming explicitly separate from both the government and Parliament. Still, they didn't move far from Britain's corridors of powers — their home is Middlesex Guildhall on the western side of Parliament Square in London.

Among its case load, the court hears appeals on cases of the greatest public importance, where it is considered there is an arguable point of law.

A Cambridge University-educated expert in family law, Hale has championed diversity in the judiciary throughout her career and has pushed for more women in senior positions. She is due to retire in January.

Hale's words in delivering the judgment were not the only issue gaining attention on social media — her striking spider brooch also generated plenty of online buzz.

Writer and art historian Anne Louise Avery wrote on twitter: "Lady Hale demonstrating the potential for vast novelistic sub-narratives offered by a correctly chosen brooch. What a tangled web we weave, indeed."

A person dressed as a caricature of British Prime Minister Boris Johnson in a prison uniform stands outside the Supreme Court in London, Tuesday, Sept. 24, 2019 after it made it's decision on the legality of Johnson's five-week suspension of Parliament. In a setback for Johnson, Britain's Supreme Court has ruled that the suspension of Parliament was illegal. The ruling Tuesday is a major blow to the prime minister who had suspended Parliament for five weeks, claiming it was a routine closure. (AP Photo/Matt Dunham)
Stanley Johnson, the father of British Prime Minister Boris Johnson gestures as he speak to the media in London, Tuesday, Sept. 24, 2019. In a setback for British Prime Minister Boris Johnson, Britain's Supreme Court has ruled that the suspension of Parliament was illegal. The ruling Tuesday is a major blow to the prime minister who had suspended Parliament for five weeks, claiming it was a routine closure. (AP Photo/Matt Dunham)