THREE judges sitting as an appeal court in Edinburgh yesterday effectively put Prime Minister Boris Johnson on notice that he must ask the European Union for an extension to Article 50 if he cannot broker a Brexit deal before October 19.

Sitting as the Inner House of the Court of Session, Scotland’s highest court, Lords Carloway, Brodie and Drummond Young accepted the promise made by the Government’s lawyers that Johnson will comply with the European Union (Withdrawal) (No 2) Act, known as the Benn Act, and seek an extension in the event of No Deal.

The judges had been asked to exercise the power of "nobile officium" – the uniquely Scottish legal authority for courts to act in the absence of a legal remedy – to sign an Article 50 extension request letter in the event that the Prime Minister refuses to do so by October 19.

READ MORE: Brexit: Court of Session delays decision on extension letter

The SNP MP Joanna Cherry QC, businessman Dale Vince OBE, and Jolyon Maugham QC of the Good Law Project brought the case after the well-publicised indications by the Prime Minister and his team that he would not comply with the Benn Act–he said he would rather “die in a ditch” than seek an extension.

On Monday, Lord Pentland refused the orders sought against Johnson, and Scotland’s most senior judge, Lord Carloway, the Lord President, and his two colleagues also refused to act instantly.

Instead they continued the case until after the October 19 deadline for a Brexit deal enshrined in the Benn Act.

The National: Lead petitioner Joanna CherryLead petitioner Joanna Cherry

Lord Carloway stated: “In this case, whether the Prime Minister will ever require to send a letter containing an extension request is uncertain.

“The UK Government and the EU may reach a deal. Parliament may approve a 'No-Deal' Brexit.

“If neither event occurs, it has not been disputed that the PM must send the letter. Until the time for sending the letter has arrived, the PM has not acted unlawfully, whatever he and his officials are reported to have said privately or in public.”

Delaying final judgement to October 21, Lord Carloway said: “If 19 October comes and goes without either of the two conditions in the 2019 (Benn) Act having been satisfied and in the absence of the letter which the Prime Minister would then be required to send, the petitioners would be entitled to return to court and seek an order ordaining the PM to comply with the terms of the 2019 Act.”

That could include the court ordering an official to send the extension letter.

Outside the court, Joanna Cherry said: “This decision is a victory for the petitioners and everyone who wants the Tory Government to obey the law, and call for an extension, so we can avoid a devastating No-Deal Brexit.

“As a result of this vital court action, the Tory Government has been forced to concede the Prime Minister will comply with the law, and promise to send a letter requesting a Brexit extension. Crucially, he has also had to admit that he will not frustrate the purpose of the Benn Act.

“The court’s decision is a clear signal it will keep a watch on Boris Johnson’s actions – and is holding a sword of Damocles over him in case he breaks his promise.

Jolyon Maugham commented: “These cases are about keeping the Prime Minister on the straight and narrow. We have extracted from him a promise that he will comply with the law.

“If he breaks that promise, he will face the music – including possible contempt proceedings. And the Courts are likely to make good any failure on his part, including signing the Benn Act letter.”

Dale Vince OBE added: “This result gives the courts the chance to jump in if the Prime Minister breaks his word.”