Boris Johnson will have to wait until early next week to learn what the Supreme Court's ruling on his decision to suspend parliament will be.

Eleven justices are preparing make a judgement on his controversial move to prorogue parliament after sitting through a three-day hearing in the UK's highest court.

The unprecedented legal case saw closing arguments delivered on Thursday, including interventions on behalf of former prime minister John Major and the Scottish and Welsh governments.

The court has been asked to determine whether or not the prorogation - which has shut down the Commons for five weeks until October 14 - was unlawful.

The case arose out of separate legal challenges in Scotland and England in which different courts reached different conclusions.

Last week, Edinburgh's Court of Session ruled the Prime Minister's action was unlawful because it was "motivated by the improper purpose of stymying parliament".

However, in a near-identical case at the High Court in London, the judge disagreed, arguing it was not a matter for the courts.

Johnson claims the five-week suspension is to allow time for his Government to set out a new legislative agenda in a Queen's Speech when MPs return to parliament next month.

But those who brought the legal challenges argue the prorogation is designed to prevent parliamentary scrutiny of the UK's impending exit from the EU on October 31.

Representing Sir John Major, Lord Garnier told the Supreme Court the former Tory PM's intervention was "nothing to do with the arguments for or against Brexit".

The "inference was inescapable" that Johnson's decision to prorogue was "motivated by his political interest in ensuring that there was no activity in parliament during the period leading up to the EU Council summit on October 17 and 18", Lord Garnier said.

At the close of the historic hearing, Supreme Court president Lady Hale said on Thursday the judges hope to give their decision early next week.

She 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."

Depending on the legal basis upon which the judges reach their conclusions, parliament may have to reconvene if Mr Johnson - who has refused to rule out a second suspension - loses the case.

The court could order parliament to be recalled, but Johnson's lawyers urged the judges to consider the "very serious practical consequences" involved in this scenario, as it would require a new Queen's Speech and state opening of parliament.

Asked shortly after the hearing ended to rule out proroguing parliament for a second time, the Prime Minister said: "I have the greatest respect for the judiciary in this country.

"The best thing I can say at the moment whilst their deliberations are continuing is that obviously I agree very much with the... Lord Chief Justice and others who found in our favour the other day."

He added: "I will wait to see what transpires."

SNP MP Joanna Cherry, who was one of the politicians who brought the Court of Session case, spoke to journalists in London's Parliament Square on Thursday.

She said: "This is a matter of legality. This is a matter of upholding democracy and a matter of upholding the rule of law."

The ruling could come at a sensitive time for Johnson as he makes his debut appearance at the UN general assembly in New York.

He is in the US from Monday to Wednesday and is expected to key Brexit meetings with German leader Angela Merkel and European Council president Donald Tusk.