The government argued that the power to make and break treaties, including the treaties that make the UK a member of the EU, is part of the royal prerogative. Prerogative powers belong to the Crown but are exercised by the government. While Parliament has removed a number of prerogative powers over the centuries, the ability to conduct international relations (including the power to make and break treaties) remains in the hands of the government. The government’s position is therefore that it has the power to trigger Article 50 without Parliament having to be involved.

While there is debate on the point, the government’s position is that Article 50 cannot be revoked once triggered. The arguments in the case, and the judgment, therefore proceeded on the premise that triggering Article 50 would inevitably lead to the loss of EU rights incorporated into UK law by the European Communities Act 1972, and so to changing domestic law.

Ciaran O’Hare of McIvor Farrell Solicitors, who acted for victims’ campaigner Raymond McCord in a separate challenge to the Brexit process in the High Court in Belfast, welcomed the ruling from London.

Mr McCord’s case was rejected by judges in Belfast and is expected to be appealed to the UK Supreme Court.

Mr O’Hare said: “We welcome today’s decision in respect of the cases before the Divisional court of England Wales. We are of the view that this is a significant decision, which will no doubt have systemic ramifications. We are currently examining the written judgment and at this stage we believe that it is supportive of our case.

“Mr McCord’s case is next listed before Belfast High Court on Tuesday 8 November 2016.”

Fergal McFerran, president of students’ movement NUS-USI, submitted evidence during the London High Court challenge on the effect the decision would have on Northern Ireland, particularly on students.

Mr McFerran’s solicitor, Darragh Mackin of Belfast firm KRW Law, said: “It is clear from today’s judgment that there is a need for Parliamentary scrutiny on an issue of such fundamental importance. As Fergal has evidenced, this is arguably of even greater significance to the people of this jurisdiction.

“The reality is legislation was introduced to create the rights afforded under the EU and only legislation can remove them.

“Parliamentary scrutiny is a minimum level of protection that democracy demands when removing such rights, and we now look forward to the next stage of this process.

“It is anticipated that the Government will seek to appeal today’s result. Any such appeal to the UKSC will be robustly defended and we intend to begin the preparation for same imminently.”