A judge in Scotland has agreed to a fast-tracked hearing on whether the British Prime Minister Boris Johnson can legally suspend parliament to force through a no-deal Brexit.
More than 70 MPs and peers have banded together to call on the Scottish courts to rule that suspending parliament to allow the UK to leave without a deal would be "unlawful and unconstitutional".
The anti-Brexit campaigners filed a petition at the Court of Session in Edinburgh attempting to block Mr Johnson from being able to prorogue parliament, and called for the case to be heard before the 31 October Brexit deadline.
At a preliminary hearing, Judge Lord Raymond Doherty agreed to expedite the timetable for the legal challenge to take place, setting the date for the substantive hearing as Friday 6 September.
Lord Doherty rejected the campaigners' attempts to have the whole hearing before one court to speed up the process, rather than the normal legal procedures.
"It's a case that requires expedition but there is a requirement for fairness to both sides," Lord Doherty said.
He announced that, under the accelerated timetable, a substantive hearing would take place on 6 September - nearly eight weeks before the Halloween departure date - with a preliminary hearing on 4 September if required to rule on any points of legal contention between the two sides.
David Welsh QC - the lawyer working for the campaigners - argued the case needed to be heard "swiftly" because any judgment that came after the date the Prime Minister has committed to leaving the EU "would be rendered academic by the passing of time".
"We are facing consequences of such extreme and severe nature that it's important for the court to fulfil its role in ruling on the law and how it should be applied," Mr Welsh said.
"There is ample evidence that the respondent will try to slow down as much as possible."
Although acknowledging the "exceptional circumstances" of the case, Lord Doherty told Mr Welsh he would be refusing the request for the whole case to be heard by just one court.
"I'm not in a position to say that this is a case to report to the inner house," he said.
"I don't doubt your intentions but these are the practicalities."
Andrew Webster QC, acting on behalf of the Advocate General, rejected the suggestion the government wanted to delay proceedings to make any judgment irrelevant if not made by the 31 October deadline.
Mr Webster argued there was "no compelling need" for the case to be heard all be the inner house that would usually deal with first appearances and appeals, rather than the outer house, which hears the arguments from both the petitioners and respondents.
"We have more than 11 weeks until October 31," he said.
"One can squeeze a lot into 11 weeks."
The legal papers, submitted by the Good Law Project acting on behalf of the politicians, state: "Seeking to use the power to prorogue Parliament to avoid further parliamentary participation in the withdrawal of the UK from the EU is both unlawful and unconstitutional."
Warning that "the exercise of the power of prorogation would have irreversible legal, constitutional and practical implications for the United Kingdom", the challenge calls for the court to declare that proroguing Parliament before October 31 would be both unconstitutional and unlawful by denying MPs and the Lords the chance to debate and approve the decision.