Northern Ireland's High Court is about to rule if parliament should vote on Brexit

The Northern Irish High Court will today deliver a long-awaited verdict on whether Theresa May's government is legally required to receive parliamentary approval before invoking Article 50.

A cross-party group of politicians launched the legal challenge earlier this month, on the basis that both UK parliament and the Northern Irish regional assembly should vote before May triggers Britain's withdrawal from the European Union.

The challenge relates to the 1998 Good Friday Agreement - a historic agreement between Britain and Ireland which crucially contains references to EU law. The agreement was a major step towards ending decades of conflict between Catholic Irish nationalists and Protestant unionists and granted Northern Irish control of its own sovereignty.

The claimants argue that the government's plans to bypass parliament and use Royal Prerogative to trigger Article 50 would be unlawful as it would mean unpicking the Good Friday Agreement without first consulting Northern Ireland.

Raymond McCord, whose son was murdered during the Irish conflict, has launched his own challenge alongside that of the cross-party group of politicians."We are confident," he said, according to Reuters.

"I believe and my legal people believe we have a very strong case."

Ronan Lavery QC, who represented McCord in the High Court, argued that withdrawal from the EU would have a "catastrophic effect" on the Irish peace process.

A lawyer defending the government told the court that using Royal Prerogative is "not illegal, unorthodox or undemocratic," while Northern Ireland's Attorney General, John Larkin QC, suggested "not one word or phrase" in the British-Irish agreement would be affected by triggering Article 50.

Earlier this month, the Royal Courts of Justice, based in London, heard a legal challenge from multiple claimants who argued it was unlawful for the prime minister to invoke Article 50 without first passing an act of parliament.

Lord Pannick QC, who was representing lead claimant Gina Miller, who BI interviewed in August, argued strongly that triggering Article 50 will mean statutory rights enjoyed by Brits as EU citizens - like the right to vote to in EU elections and refer a legal dispute to the European Court of Justice - will be destroyed in an instant.

A verdict in the Northern Irish case is expected shortly after 10.00 a.m. BST (5.00 a.m. ET).