Gina Miller, the woman who derailed Theresa May's Brexit

The Prime Minister's plans for leaving the European Union are in tatters this morning after the result of one of the most divisive referendums in recent history was taken to London’s High Court.

Gina Miller, a philanthropist and co-founder of the London-based investment fund manager SCM Private, was the lead claimant in a challenge heralded as one of the most important constitutional cases in generations.

She challenged Theresa May’s bid to avoid a parliamentary vote on triggering Brexit, arguing that using the Royal Prerogative to invoke Article 50 to leave the European Union without asking MPs to approve it is unconstitutional.

This morning, Lord Chief Justice Thomas and two other senior judges agreed the Prime Minister does not have the power to trigger Article 50 without a vote from Parliament.

Her challenge was heard at the High Court in London where she was represented by QC Lord Pannick, a renowned human rights lawyer.

Speaking outside of the High Court, Ms Miller said she was “delighted” by the decision and hoped the Government would “make the wise decision of not appealing”. She was greeted by a round of applause from the crowds.

Her statement in full:

“This result today is about all of us: our United Kingdom and our futures.

“It is not about how any of us voted – each of us voted to do what we believed was the right thing for our country.

“This case is about process, not politics. My dedicated legal team – Mishcon de Reya and counsel – are, alongside myself and my supporters, pleased to have played our part in helping form a debate on whether the rights conferred on UK citizens through Parliament legislation 44 years ago could be casually snuffed out by the executive without Parliament or our elected representatives and without proper prior consultation about the Government’s intentions for Brexit.

“However you voted on 23 June, we all owe it to our country to uphold the highest standards of transparency and democratic accountability that we are admired and respected for around the world.

“Thank you very much.”

What were her reasons for launching this challenge?

Ms Miller broke down her argument during an interview with Audio Boom.

She was unsatisfied with Ms May’s announcement that there would be a debate on the issue, dismissing it as merely “political blustering”.

“They can use this very antiquated, secretive Royal Prerogative to bypass Parliament. You have to question how they can possibly bypass a sovereign parliament? Surely that’s what we wanted, was a sovereign Parliament?

“I’m questioning whether the Government has the right to bypass Parliament and use this royal prerogative, which they are still saying that they do and that she does, and that she and a handful of ministers will be able to trigger Article 50 without any sort of legal certainty or scrutiny in Parliament.”

She said her case was not about delaying the decision and should not affect the timetable currently in place for triggering Article 50. Instead, she is focusing on ensuring the UK’s sovereignty is not compromised.

“I don’t want a precedent set which says a prime minister and a handful of MPs or ministers can take away or grant rights.”

What has the reaction been?

While Ms Miller has enjoyed support from those wishing to remain a part of the EU, her legal challenge has come at a personal cost. The High Court has heard how Ms Miller received “abuse, threats and insults” after launching her action.

Her position on whether Britain should leave or remain is not as cut and dry as her legal challenge might indicate

Ms Miller told Business Insider: “Actually, I managed to fall out with both sides – Leave and Remain. I thought the question was far too binary and I kept saying I was not a remainer – I was for Remain, reform, and review.

“I thought the question was far too binary. While I agree that we should remain, I don't believe that it's something to be taken for granted.”

Ms Miller, 51, was born in Guyana and raised in the UK. She launched Miller Philanthropy in 2009 and has contributed to the Margaret Thatcher infirmary at the Royal Hospital Chelsea, as well as to other charitable causes.

This article appeared in its original form on 14 October. Additional reporting by agencies