The documents which have now been released show how Government lawyers intend to argue that it is “constitutionally impermissible” for the devolved regional parliaments or Westminster to be given the authority to decide when and how Article 50 should be triggered. They say: “The appropriate point at which the UK should begin the procedure required by article 50 to give effect to [informing the UK’s withdrawal] is a matter of high, if not the highest policy. “It is a polycentric decision based upon a multitude of domestic and foreign policy and political concerns for which the expertise of ministers and their officials are particularly well-suited and the courts ill-suited.”

The Government also argued that, to the extent the issue can be ruled on by the courts, the “commencement of the process of withdrawal from the EU” does not itself bind or change any law or statute – such changes would be subject to Parliamentary scrutiny and legislation.

People’s Challenge has told the court they are arguing the UK’s constitutional arrangements mean that only parliament can lawfully ‘decide’ to leave the EU for the purposes of Article 50; and that [David Davis, the Secretary of State for Exiting the EU] may only ‘notify’ such a decision to the European Council under Article 50(2) TEU once he has been properly authorised to do so by an act of parliament.”