UK Prime Minister Theresa May announced in early October that her government would formally notify Brussels of the United Kingdom's intention to leave the European Union by triggering Article 50 of the Treaty of Lisbon by the end of March.

The government said the decision to leave the EU was taken by the public in the referendum on June 23 and that its executive powers, under the royal prerogative, were sufficient to give notice to the EU on behalf of the cabinet.

But on Thursday, the UK's High Court ruled the government does not have the power to begin the formal process of leaving the EU without the approval of parliament. This has created even more uncertainty.