The Government has lost its historic battle in the Supreme Court over Brexit.
The highest court in the land rejected an appeal by ministers against a High Court judgment blocking their decision to begin Britain's exit from the European Union without Parliament having a say.
Supreme Court justices ruled, by a majority of eight to three, that Prime Minister Theresa May cannot lawfully bypass MPs and peers by using the royal prerogative to trigger Article 50 of the Lisbon Treaty and start the two-year process of negotiating the UK's divorce from its EU partners.
The ruling is a blow to Mrs May, who has repeatedly said she intends to trigger Article 50 by the end of March following the clear majority in favour of Brexit in the June 2016 referendum.
It was won by a wide-ranging group of anti-Article 50 campaigners led by investment manager Gina Miller, 51, and hairdresser Deir Dos Santos.
What does the judgement mean?
While the court agreed that the Government do generally have "prerogative" power - the power to act without consulting parliament.
But the Supreme Court decided that in this case the government must pass an act of Parliament to trigger Article 50 .
Their main reason was that when the UK joined the EU, the Union was able to create UK laws - and that can only be reversed with legislation.
They also decided an act of parliament would be necessary because the rights of UK citizens would change.
Does this mean we won't be leaving the EU?
What happens next?
The Government must come forward and pass a law to trigger Article 50 .
MPs and peers will be given a chance to debate, scrutinise and vote on the bill when it comes to Parliament.
But it's thought the bill could be just two clauses long, which leaves little scope for MPs to offer amendments to the details.
How long will the process take?
Theresa May says even if Parliament does vote on Article 50 , she still intends to trigger it before the end of March.
After that, the UK will remain a member for a period of two years before breaking away entirely from the EU.
Negotiating deals with EU members and others could take years after that
Will Scotland and Wales get to vote on it?
The Supreme Court decided unanimously that it was for the UK parliament to vote on Britain's relationship with the EU, and it shouldn't be devolved to the regions.
This will be a blow to Scottish First Minister Nicola Sturgeon, who has said she wants Scotland to remain in the EU even when the Union exits.
Will MPs and peers get a vote on Theresa May's deal?
Yes. Theresa May has confirmed MPs will get to vote on the deal she manages to eke out with Brussels on Britain's relationship with Europe after Brexit.