The woman who led the legal battle against the British government's ability to push forward with Brexit has reacted to a high court decision in her favour.

Britain's High Court ruled on Thursday that the prime minister cannot trigger the UK's exit from the European Union without approval from Parliament

Financial entrepreneur Gina Miller, who supported the campaign to stay in the European Union, brought the case.

She argued that leaving the EU would deny her fundamental rights, such as the right to free movement and freedom of services across Europe.

The case is considered the most important constitutional matter in a generation.

It centres on whether Prime Minister Theresa May can start negotiating Britain's exit from the EU without a vote in the House of Commons.

At the core of the matter is the balance of power between Parliament and the government.

Regardless of the victor, the case will likely be immediately appealed to the Supreme Court.

May has said she will invoke Article 50 of the EU treaty - triggering two years of official exit talks - by March 31.

London - 3 November 2016

1. Gina Miller exiting High Court

2. SOUNDBITE (English) Gina Miller, financial entrepreneur who led legal Brexit battle:

"A few words: the result today is about all of us. It's not about me or my team. It's about our United Kingdom and all our futures. It's not about how anyone voted. Every one of us voted for the best country and the best future. This case was about process, not politics. My dedicated team at Mishcon (legal team), and counsel and I are absolutely delighted that we've been able to be part of this debate, and to bring some sobriety as we go forwards. The judgement, I hope, when it's read by the government - and they contemplate the full judgement - that they will make the wise decision of not appealing, but pressing forwards and having a proper debate in our sovereign parliament, our mother of parliaments that we are so admired for around the world. Thank you."

Britain's government must get parliamentary approval before starting the process of leaving the European Union, the Supreme Court ruled on Tuesday.

The decision potentially delays Prime Minister Theresa May's plans to trigger exit negotiations by the end of March.

London - 24 January 2017

1. Various of Parliament

2. Evening Standard newspaper vendor talking to security officer

3. Close of Evening Standard newspaper, reading (English) "Judges' blow to May over Brexit."

4. Vendor and security officer talking

5. Close of newspaper lead, reading (English) "PM can't trigger Article 50 without Parliament backing, says supreme court in historic ruling."

In a major blow for Britain's government, the High Court said the prime minister can't trigger the UK's exit from the European Union without approval from Parliament.

The government is likely to appeal Thursday's ruling to the Supreme Court.

Claimants argue that leaving he EU will remove rights, including free movement within the bloc, and say that cannot be done without Parliament's approval.

Gina Miller, financial entrepreneur and the lead claimant in the High Court case, said the proper place for a debate on leaving the EU is in a sovereign Parliament.

Prime Minister Theresa May says the June 23 referendum on EU membership gave her a mandate to take Britain out of the 28-nation bloc.

London, UK - 3 November, 2016

1. Financial entrepreneur and the lead claimant in the High Court case, Gina Miller, talking to the media outside court

2. SOUNDBITE: (English) Gina Miller, financial entrepreneur, lead claimant:

"I think at the end of day the days of victory are always great but it's actually the days after that count and it's now to the government what they do and I hope the MPs will do their job and actually debate this in a sober, grown up way because leading up to the vote we did not have sober, honest, rational debates so it's now over to the politicians."

3. Cutaway of media

4. SOUNDBITE: (English) Gina Miller, financial entrepreneur, lead claimant

"It is my hope that the government doesn't appeal."

5. Claimant Charlie Mullins outside court

6. SOUNDBITE: (English) Charlie Mullins, managing director Pimlico Plumbers, claimant

"Well as I say it took three minutes for the three highest judges in the country to sum up who's right or wrong to trigger article 50. I think it was a no-brainer anyhow, that's why we have Parliament, they make all the rules and regulations, why would you let the government overrule them and it was clearly shown today. I think it was a great result and whatever happens this wasn't against the referendum, this was all about article 50 and I think it's been proven today what the decision is made is the correct one."

7. Sign reading: (English) "Royal Courts of Justice"