BORIS Johnson could be asked to return to the Commons next week if a ruling by Scottish judges that his advice to the Queen to suspend Parliament was unlawful is upheld.

The development emerged yesterday at the close of a historic three-day legal battle at the UK’s highest court which was hearing appeals against two earlier judgements over the prorogation of Parliament until October 14, including on one case spearheaded by SNP MP Joanna Cherry.

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During the closing stages of his submission, Lord Pannick – the QC representing anti-Brexit campaigner Gina Miller – told the Supreme Court in London that the Speakers of the Commons and Lords could reassemble parliament if they found that the Prime Minister’s advice to the Queen was illegal.

He went on to argue that, even if Johnson did not act, the Speaker and the Lord Speaker could do so.

The decision on the ruling and what course of action could be taken will now be considered by the 11 Supreme Court judges, with their judgment being published early next week.

Lady Hale, president of the Supreme Court, said: “I must repeat that this case is not about when and on what terms the United Kingdom leaves the European Union.

“The result of this case will not determine that. We are solely concerned with the lawfulness of the Prime Minister’s decision to advise Her Majesty to prorogue Parliament on the dates in question.

“As we have heard, it is not a simple question, and we will now carefully consider all the arguments that have been presented to us.

“We hope to be able to publish our decision early next week.”

The National: Anti-Brexit campaigner Gina Miller has also sought to challenge the prorogationAnti-Brexit campaigner Gina Miller has also sought to challenge the prorogation

During a discussion on what remedy, if any, the court could provide, Lady Hale said: “Well, we will have to decide what the answer is and we will have to decide one way or another what the consequences of that are.”

She added: “None of this is easy.”

This week’s Supreme Court case has centred on two appeals – one by the UK Government challenging the Court of Session ruling that the Prime Minister’s advice was unlawful, and a second, a challenge by Miller to a High Court ruling that the issue over prorogation was not a matter for the court to settle. Miller’s appeal has been backed by former prime minister Sir John Major.

But in a further twist, the UK Government yesterday argued that even if the Prime Minister loses the case Parliament could remain suspended.

Documents submitted to the court by Sir James Eadie QC and Advocate General for Scotland Lord Keen on behalf of the Prime Minister revealed a number possible scenarios.

The first envisages a situation where the judges find the prorogation was unlawful, but their reasoning leaves open the possibility that Parliament could be prorogued for five weeks in a lawful manner. A second possible outcome is that the court could find the suspension was unlawful and that the recall of Parliament before October 14 is the “only option lawfully open to the Prime Minister”.

Lord Advocate James Wolffe QC, on behalf of the Scottish Government, told the judges yesterday that the prorogation was taking place during a “time-critical period” when the UK Government’s decisions are likely to have “momentous consequences”.

Lord Garnier QC, representing Sir John Major, said his client had made “a clear and unambiguous allegation in evidence that the reasons [for prorogation] set out in the documents put before the court by the prime minister cannot be true”.

He added: “Where an allegation of this kind has been made, it would be normal for there at least to be some kind of witness statement.”

Lord Garnier said prorogation did not just stop Parliament from sitting, but prevented it from carrying out other functions – including its ability to find people in contempt.

He told the court people who have been found in contempt of Parliament in recent years included Johnson’s senior adviser, Dominic Cummings.

Johnson’s lawyers urged the court to consider the “very serious practical consequences” as the recall of Parliament would require a meeting of the Privy Council and a new Queen’s Speech.

They also assert that, depending on the court’s reasoning, it may still be open to the PM to consider a further prorogation.

Lord Keen said the issue of prorogation was “a matter between the executive and Parliament”, adding that if Parliament “takes exception” to actions of the executive “they have the tools available”, namely a motion of no confidence.