Aidan O'Neill QC, repesenting Joanna Cherry QC, is defending their win against the prime minister at the court in Edinburgh.

He is explaining why the Scottish court ruled that Parliament's suspension was unlawful, claiming an advantage of being "400 miles away" from the Westminster "bubble".

Image source, UK Supreme Court

Mr O'Neill, who wants the Scottish court judgement upheld, commends the approach taken by the Inner House at Edinburgh's Court of Session, which made the ruling.

He says the court was acting to protect the constitution - and adds this is also the role of this court.

He goes on to say history is important in the case, joking that the key dates in English history were "1066 and 1966".

One of the judges quips back that Mr O'Neill might need to explain why 1966 was important - especially for a Scot.

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How does the Supreme Court work?

Back in June, President of the Supreme Court, Baroness Hale, who’s overseeing proceedings on the prime minister's decision to suspend Parliament, gave a rare interview to @EmmaBarnett, external.

Click here to listen to the full interview on BBC Sounds.

Image source, UK Supreme Court

Aidan O'Neill has begun making his submissions.

He's the lawyer for the group, led by SNP MP Joanna Cherry, who brought the Scottish case to court. The Scottish court ruled that the suspension of Parliament was unlawful.

The government appealed this to the Supreme Court, and Mr O'Neill is arguing against them.

Dominic Casciani
Home Affairs Correspondent

If Boris Johnson loses, the question then would be what kind of action the court orders.

If the judges rule that prorogation was legal, Parliament will remain shut until 14 October - unless the government advises the Queen to recall MPs at an earlier date.

Gina Miller's lawyers are, however, asking the justices for a repeat of the declaration from Edinburgh's Court of Session that the prime minister's actions were "null and void and of no legal effect".

If her side wins, it's still unclear how and when Parliament would resume - whether MPs could simply return to the Commons, or if they would need to be recalled by the Queen on the advice of Mr Johnson.

Image source, PA Media

The Supreme Court is considering whether Boris Johnson's decision to suspend Parliament for five weeks was legal.

After an English and a Scottish court came to different conclusions, 11 Supreme Court justices will give a final ruling.

They have to answer two questions:

First, do judges have the power to intervene in how a prime minister prorogues Parliament?

And, if they do, was Edinburgh's court right to conclude Mr Johnson had acted unlawfully in closing it for five weeks?

Read more about how the Supreme Court works here.

Today we've heard from the respondents - those who are defending the appeals and want them to be upheld.

That will continue this afternoon as we hear from Aidan O'Neill QC, the lawyer for the group, led by SNP MP Joanna Cherry, who brought the Scottish case to court.

If you need a reminder, last week Scotland's highest court ruled the five-week suspension was "unlawful".

The government appealed this to the Supreme Court, and Mr O'Neill will be arguing against them.

He'll be talking for two hours.

The government's lawyer, Sir James Eadie QC, argues that the decision to suspend Parliament is not one for the court to decide on.

He says that prorogation power had been "expressly preserved by Parliament".

Image source, EPA

The Supreme Court's 11 judges began sitting at 10:30 BST, starting with two-and-a-half hours of arguments from the government's representative, Sir James Eadie.

He argued the suspension of Parliament was "the territory of political judgements not legal standards".

The prime minister's decision was not for the court to decide on, he said.

Sir James argued Parliament had previously passed laws addressing aspects of prorogation, but there was no law relevant to this particular case.

Therefore, he said, the courts could not intervene in the decision.

The hearing will resume at 14:00 BST.

Image source, PA Media

As arguments continue in the Supreme Court, and uncertainty over Brexit prevails, Poland's ambassador to the UK has said it might be best for Polish nationals to return home after Brexit.

Arkady Rzegocki has written to 800,000 Poles in the UK, advising them to "seriously consider" leaving the country.

He said living standards in Poland were improving, providing "a very good opportunity to come back".

Read more from Poland's ambassador here.

The morning session of the second day of the hearing has ended, as judges and lawyers head for lunch.

The hearing will resume at 14:00 BST, when it's time for lawyer Aidan O'Neill QC to start making his submissions.

Mr O'Neill is representing the cross-party group of politicians, led by Joanna Cherry, who won a case in Scotland's highest court. The Scottish court ruled that Boris Johnson's suspension of Parliament was unlawful. The UK government wants to overturn that Scottish ruling, but Mr O'Neill is trying to uphold it.

Image source, UK Supreme Court

Sir James, arguing that the judges should uphold the High Court's ruling that Boris Johnson's suspension of Parliament was lawful, argues against the other side's suggestion that Mr Johnson used the power to prorogue improperly.

He says the documents provided (including a No 10 memo) show this.

"We respectfully submit that it does appear that there were a myriad of reasons for the length - which is truly what we're arguing about - of this prorogation," he says.

"In truth and in fairness, reading those documents, the evident aim was tolerably clear and everyone, in particular the prime minister, was concerned to get to a place where a Queen's Speech was produced."

He adds the government "recognised that prorogation had the effects that it was going to have" and they "recognised the central planning assumption to get to the Queen's Speech was incredibly tight anyway and a period of five weeks was the minimum that would be required to get there".

Image source, UK Supreme Court

Supreme Court Judge Lord Wilson says it is 'odd' that there are no signed witness statements accompanying all the documents the government has submitted to make its case.

He speaks after Sir James, the PM's lawyer, says that it is "plain" from the documents - such as the memo from former No 10 official Nikki da Costa and comments by the PM during Cabinet - that "there was real concern to ensure Parliament had sufficient opportunity to debate these matters".

Sir James adds: "If the basic attack was this was improper motive... because it was designed to stymie parliament, we respectfully submit that is unsustainable".

And he tells the judges the documents include minutes from Cabinet - which he says is rare.

But Lord Wilson, comes back at Sir James, mentioning the lack of a witness statement from the prime minister.

"No one has come forward from your side to say this is true. We're just given the documents... floating around.

"Isn't it odd that nobody has signed a witness statement to say, this is true, these are the true reasons for what was done?"

Sir James replies: "You have the witness statement you have."

He says it's up to the court to make a judgement on the basis of documents, which include briefings directly to the PM.

"No one has suggested they are not proper documents," Sir James adds.

Dominic Casciani
Home Affairs Correspondent

Sir James Eadie argues that the desire to ensure “responsible government” is not a legal justification for interfering with a PM’s power to close down Parliament.

“How do you determine the standard,” he asks. "What is responsible and what isn’t?"

Lord Kerr is pushing Sir James, for the PM, yet again on the practical effect of the prorogation.

He asks why Parliament could not have simply gone into recess, rather than be prorogued. Recess is a pause for party conference season, but MPs could return at a moment’s notice.

Sir James says that was possible but irrelevant. Parliament did in fact pass a no-deal delay bill - but also did nothing to bring a no-confidence vote and other steps being suggested to block Boris Johnson’s Brexit strategy.

Sir James starts on some of his final points - before the lunch break at 13:00 BST.

"Parliament has been considering Brexit for months and years," he says - adding that it's been able to make legislation during this time, and has done so.

"We saw from the debate yesterday that few sitting days had in fact been lost, in comparison with recess," says Sir James.

Former chancellor and current Evening Standard editor George Osborne says that if, as BBC political editor Laura Kuenssberg has been told by a source, the government is right in thinking the Supreme Court is leaning toward saying prorogation is justiciable (in other words, it is a matter for the courts), then the PM's plan may be unravelling.

Dominic Casciani
Home Affairs Correspondent

The exchange between Lady Black and Sir James Eadie - and the earlier intervention from Lord Sales - feel important.

They both go to a wider concept of parliamentary supremacy than the one the government is promoting.

The government in essence is telling the court that parliamentary sovereignty means the right to make/break laws and that’s about it.

Opponents say sovereignty also means the right to take any steps necessary to hold an allegedly dodgy prime minister to account.

Image source, UK Supreme Court

Responding to a question, Sir James - who is acting for the government - argues that the length of prorogation "is not just restricted to how long you need to do a Queen's Speech".

"Prorogation can exist in a whole variety of different contexts," he adds, adding a "double prorogation" can also exist.

He later moves on to the argument, which he has already mentioned, that Parliament could have taken action to prevent it being prorogued.

Sir James tells the judges: "Parliament had the opportunity, if it had wished to do so, to legislate not merely to control the perceived undesirable consequences of a no-deal Brexit.

"It could have said, and by the way, if and to the extent Parliament is going to be prorogued next week, we think we need more time. But it didn't do that."

David Allen Green - a legal columnist for the Financial Times - says that, having heard arguments from both Lord Pannick (on behalf of Gina Miller) and Sir James Eadie (on behalf of the PM), neither side appears a clear winner.

Dominic Casciani
Home Affairs Correspondent

We’ve witnessed a very interesting exchanges in the last five minutes.

Lady Black asks the PM's man Sir James Eadie: If prorogation has removed Parliament from the picture, and courts have no role in this, how can Parliament apply a check and balance on the power used to close it down?

Sir James replies that he acknowledges prorogation prevents Parliament sitting, holding committees and hauling ministers to the House to answer questions. But after prorogation they can resume that work and even go for a no-confidence vote.

Lady Black then replies: How does that help in a time-sensitive situation, when time has been lost? (Remember: Parliament is prorogued until 14 October and Brexit is scheduled for 31 October.)

Sir James says Parliament can resume and do what it wishes and resume all the forms of control it had before.