SNP MP Joanna Cherry says a Scottish court has left Boris Johnson with a "Sword of Damocles" hanging over his head should he break the law by failing to seek a Brexit extension if no deal is reached with the EU.

Campaigners including Cherry welcomed a decision by judges at the Court of Session in Edinburgh to monitor whether the Prime Minister abides by the Benn Act.

The court delayed ruling on a legal bid aimed at forcing Johnson to send a letter if no withdrawal deal is reached by October 19. It will continue the case on October 21.

The Benn Act, passed by MPs in a bid to prevent a no-deal departure, obliges the Prime Minister to ask for an extension to Article 50 rather than leave without a deal.

The campaigners asked the court to use the power of "nobile officium" to allow an official to send a letter on behalf of Johnson if he refuses to do it himself.

Three senior judges said the political debate must be played out before any decision is made, and delayed their ruling so campaigners do not have to start new proceedings if circumstances change.

READ MORE Court of Session delays ruling on Brexit extension letter

Cherry is leading the challenge along with fellow QC Jolyon Maugham and businessman Dale Vince.

She 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.

"The Tory Prime Minister must obey the law and call for an extension, or face the consequences - including the ability for Scotland's supreme court to force a request for an extension."