A Supreme Court decision on whether Prime Minister Boris Johnson's suspension - or proroguing - of Parliament was lawful or not is expected to be announced later this morning.
The highest court in the UK consisting of 11 justices - the largest group possible - will rule on whether the decision to suspend Parliament for five weeks was lawful.
Ministers had claimed it was not a court matter, but critics said it was a move which was motivated by a desire to limit scrutiny of the Prime Minister's Brexit plans.
A judgement is expected at around 10:30 am on Tuesday. If the ruling goes against Mr Johnson, it could lead to Parliament being reconvened with immediate effect.
The government has indicated that it will "abide by" the Supreme Court ruling.
The Prime Minister is in New York for the UN climate conference where he has refused to rule out seeking to prorogue Parliament for a second time if the ruling goes against him.
Under the current arrangements, Parliament is due to return on October 14th following the suspension, with the UK schedule to leave the European Union on October 31st.
The Supreme Court sat last week over three days to hear two appeals - one from campaigner Gina Miller - and the second from the government.
Ms Miller was appealing against the High Court in London's decision that prorogation was "purely political" and not a matter for the courts.
Her challenge was supported by former PM Sir John Major, shadow attorney general Baroness Chakrabarti and the Scottish and Welsh governments.
Separately, the government was appealing against a ruling by the Court of Session in Edinburgh that prorogation was "unlawful" and had been used to "stymie" Parliament.
The challenge in the Scottish Court was brought by a cross-party group of MPs and peers led by Joanna Cherry, of the SNP.
The Supreme Court has been hearing legal arguments from the English and Scottish court cases before the government's lawyers had an opportunity to respond.
Read more of today's stories here
Mr Johnson has indicated that he is going to "wait and see" what the Supreme Court judgement is and clearly stated the government "fully respects the law and fully respects the judiciary." He described the judiciary's independence as "one of the glories of the UK."
During the proceedings last week, government lawyer Lord Keen QC said it was "forbidden territory" for judges to intervene on political arguments over when and how Parliament is suspended.
However, Lord Pannick QC for Ms Miller said the "exceptional length" of the prorogation was "strong evidence" the PM's motive was to "silence Parliament", which he saw as an obstacle to his political aims.
Mr Johnson said he was proroguing Parliament so that a new Queen's Speech could be held on October 14th to outline the goverment's legislative proposals for the year ahead.
