Raymond McCord; part of a group making a legal challenge against British plans to leave the European Union without a vote in the Westminster parliament; departs the High Court in Belfast, Northern Ireland October 4, 2016. Clodagh Kilcoyne/Reuters The Northern Irish High Court has ruled that Theresa May's government does not need to secure the approval of UK parliament before triggering Britain's exit from the European Union.

In a summary delivered at around 10:30 a.m (BST), the High Court rejected the claim that the UK government cannot use Royal Prerogative to invoke Article 50.

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

The challenge related to the 1998 Good Friday Agreement — a historic agreement between Britain and Ireland which 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 suggested that the government's plans to bypass parliament and use Royal Prerogative to trigger Article 50 was unlawful as it would mean unpicking the Good Friday Agreement without first consulting Northern Ireland. Around 56% of Northern Irish voters backed Remain in June's in-out referendum.

Raymond McCord, whose son was murdered during the Irish conflict, launched his own challenge alongside that of the cross-party group of politicians."We are confident," he told Reuters before entering court.

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

However, judges at the High Court in Belfast rejected the claim on Friday morning, marking a key victory for the UK government in one of many legal battles it faces over Britain's departure from the 28-nation bloc. All of the claimants' arguments were rejected.

May's government cannot relax just yet, though.

Earlier this month, the Royal Courts of Justice, based in London, heard a strong legal challenge from 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.

The judges who heard this case are expected to give their verdict next month.