The already divisive issue of Brexit has been notched up a gear with the beginning of a Supreme Court appeal against a ruling that Parliament must vote on starting EU exit negotiations.

UK Prime Minister Theresa May plans to trigger Article 50 formally beginning the two-year-long divorce proceedings by the end of March.

However, last month three High Court judges ruled that only Parliament has the authority to begin talks to leave the Union.

The government claims the law is being misinterpreted and is appealing the decision.

Opposing groups of campaigners gathered outside the UK’s highest court in London as an expected four days of hearings began. A verdict is expected in January, 2017.