UK Prime Minister Boris Johnson. Photo: VCG

The legal case to decide whether Prime Minister Boris Johnson acted unlawfully when he suspended the British parliament drew to a close Thursday in London.

But Johnson will have to wait until early next week to hear the judgment of the Supreme Court, the highest court in Britain.

In a major boost for embattled Johnson, President of the European Commission Jean-Claude Juncker said Thursday that a Brexit deal is possible by the end of October.

British pound climbed to its highest level in months against the US dollar after his announcement.

For three days, top lawyers representing both sides have weaved their way through a maze of legal cases to contend respectively.

Law experts monitoring the landmark case are divided on the likely outcome. Early next week Lady Hale, president of the Supreme Court, will announce the decision of the 11 judges who have been listening to the legal submissions.

If the judges rule, either unanimously or by a majority, that Johnson was acting within his rights, the focus will switch to the grand occasion of a State Opening of Parliament on Oct. 14 by the British monarch.

But government managers were last night pondering on what Johnson should do if the judges rule against him and decide he should not have suspended parliament.

The case and the decision next week come at a time when the House of Commons is suspended anyway, to enable politicians to attend their respective party conferences.

This week the minority Liberal Democrats have been holding their annual rally in Bournemouth. This weekend hundreds of politicians from the main opposition Labour Party will head to the southern English resort of Brighton for their conference. And a week later Johnson will make his first keynote conference speech as prime minister at the Conservative pow-wow in Manchester.

It means the Commons would have in any case been shut until early October.

But in the closing speeches in the Supreme Court, barrister Lord Pannick said if the government loses the case, parliament should resume as soon as possible next week.

Pannick, the barrister representing main appellant, the businesswoman and Remain campaigner Gina Miller, sought a declaration that Johnson's advice about the suspension was unlawful.

Pannick asked the court to draw the inference that the length of the suspension was influenced by Johnson's desire to stop parliament obstructing his policies.

"There is no other rational reason for the length of the prorogation," he said, adding that would amount to an improper purpose.

Lord Keen, representing the British government, said that prorogation, or suspension of parliament, could be done for political purposes.

He told the judges: "If parliament wants to block prorogation, it can move a motion of no confidence. That will be debated if it is tabled by the leader of the opposition." He added that no such call for a debate had been demanded after Johnson's announcement.

Keen said it is for parliament and the executive to determine whether prorogation is proper, adding that if the court were to start ruling on prorogation, it would be entering "a minefield."

Early Thursday the court witnessed the spectacle of the current Prime Minister Johnson being taken to task by former Conservative prime minister John Major. Major moved into 10 Downing Street in 1990, succeeding Margaret Thatcher who had governed for 13 years.

In a written submission to the court, Major said Johnson's reasons for suspending the Parliament cannot be true.

Major said Johnson had ulterior motives for suspending Parliament.

He said if the Supreme Court rules in favor of Johnson it would risk allowing a prime minister to suspend parliament in future for any reason.

He said that in such circumstances, a prime minister opposed to a standing army could prorogue in order to disband the military, or suspend Parliament ahead of facing a vote of confidence vote.

The case ended up in the Supreme Court because the highest court in Scotland ruled that Johnson had acted unlawfully, while the High Court in England decided in favor of Johnson.

Critics both inside and outside of parliament also have contended that the shutdown was geared to stymie debate in parliament about Brexit.

Away from the court house, Johnson's insistence that Britain will leave the EU with or without a deal on Oct. 31 continued Thursday to dominate the Brexit skyline.

Johnson has also insisted that he will not ask Brussels for an extension of Britain's membership, even though the Houses of Parliament have passed a bill forcing him to do so.

In an interview Thursday with Sky News, the President of the European Commission Jean-Claude Juncker said a Brexit deal can be done with Britain before the October deadline.

Juncker said a no-deal Brexit would be catastrophic for both the UK and the EU, adding that a deal was possible before Oct. 31.

Juncker confirmed that the British government has submitted a proposed deal to replace one agreed with Johnson's predecessor Theresa May. Her deal was rejected three times by the House of Commons, mainly because it included a so-called backstop, a mechanism to avert a hard border between Northern Ireland and the Irish Republic.

Juncker said the basis of a deal would revolve around Northern Ireland remaining within EU rules on food and agriculture, with checks taking place away from the Irish border.

Asked if the chance of a deal was more than 50/50, Juncker replied that he did not know, but added "we can have a deal".

"This was a rather positive meeting, although the British press was reporting it in the other way. We can have a deal," Juncker told Sky News.