Image source, bbc

What would the question be?

This would also be the subject of intense negotiation, should we get that far. The  draft referendum bill  put out for consultation in 2016 was based on a question matching that approved by the Electoral Commission in 2014: "Should Scotland be an independent country?"

The UK government might argue for a Remain/Leave style question, like that of the EU referendum.

Again, Ms Sturgeon wants Holyrood to have the final say, but she acknowledges that the Electoral Commission could intervene.

SNP MSP Clare Adamson says asks Labour if they are intent to leave Scotland to the vagaries of a Tory government. 

Ms Adamson says the Tory government have a cheek to say that the SNP are divisive. 

The SNP MSP says the Lib Dems want to give choice for the UK but not choice for Scotland.

"This is the future of our country," she says. 

Labour MSP Jenny Marra raises a point of order to say SNP MSP's Christina McKelvie and Richard Lyle got well over seven minutes in this debate and that should be extended to all members.

Deputy Presiding Officer Linda Fabiani says it is not a point of order and the timings of debate are set out by the business bureau. 

SNP MSP Richard Lyle raises a point of order to say he has not yet spoken in this debate. 

Labour MSP Jenny Marra says "it is with a heavy heart that we come to this debate again." 

"Those of us that voted no in 2014 did not expect to be here again because we were promised it would be once in a generation," she says. 

Ms Marra says an independent Scotland would find it difficult to become a member of the EU given that all its members would have to agree. 

"Scotland would struggle to meet the requirements," she says. 

The Labour MSP says "the idea that Scotland could take over the UK's membership is at best naive."

Ms Marra says the SNP have taken almost £900 per pupil out of Dundee schools. 

Labour MSP Monica Lennon intervenes, saying she is blocked on twitter and asks if Christina McKelvie will maintain her record as the politician that tweets Wings over Scotland most.

Ms McKelvie responds saying if anyone looks at the public record they will know why Monica Lennon and her abusers are blocked on twitter.

Labour MSP Daniel Johnson raises a point of order saying describing members as "abusers", surely cannot be in order.

Deputy Presiding Officer Linda Fabiani says: " If you wish to make a complaint Mr Johnson, I think you should do so."

Image source, bbc

Ms McKelvie says she did not refer to any single member, "but there is a cohort".

Lib Dem MSP Mike Rumbles also raises a point of order saying it is unacceptable for a member to point at the Labour members and call them a "cohort".

Ms Fabiani says members should always treat each other respectfully and the record will be checked.

Ms McKelvie closes saying: "If the choice is bombs not bairns, I choose bairns."

Image source, AFP Getty

Fancy a flutter? Here are the odds

Most bookmakers responded to Ms Sturgeon's announcement by making an independence vote the odds-on favourite result of the next referendum.

Ladbrokes had Yes to independence at 8/11, with a No vote at 11/10, while William Hill also had No at 11/10 and Yes at 4/6 - with Coral offering the exact same odds.Paddy Power had a pro-independence vote at 1/2, with odds of 6/4 on there being a vote in favour of remaining in the UK.

However, Paddy Power had 2020 or later as the clear favourite in terms of when the vote is held, with odds of 4/7, while the last three months of 2018 is at 7/1.

After Mrs May's announcement, Paddy Power cut odds of a referendum in 2020 or later to evens, while they put the odds of a pro-independence vote at 4/7.

Image source, bbc

SNP MSP Christina McKelvie says Theresa May is a "tin-eared leader" and is unwilling to make any compromise.

Ms McKelvie says: "People voted last time because they thought they were safe in the EU."

She says: "We are the voice of the people, because we are the government of the people."

The SNP MSP says the prime minister does not want indyref2 at all and certainly not before her "dog-Brexit deal" is completed.

She says the electorate must be given the right to choose their future.

Repeated attempts at an intervention are met with Theresa May's phrase: "Now is not the time."

What do the polls say?

In the immediate aftermath of the Brexit vote, there was a bounce in the polls in favour of Scottish independence. But this quickly fell away to leave  levels of support roughly where they were  at the last referendum.

But more recently, an Ipsos Mori poll for STV found that  respondents likely to vote were split 50-50, external .

And a BMG  survey for the Herald, external  on the eve of Ms Sturgeon's announcement suggested support for the Union is still narrowly ahead, at 52% to 48%.

The Scottish Social Attitudes Survey found support for independence  at an all-time high  - but it also found the popularity of the EU had fallen, with Eurosceptism higher than ever.

Image source, bbc

Conservative MSP Donald Cameron says: "The SNP's shameless hypocrisy needs to be called out."

Mr Cameron accuses the SNP of using Europe as a tactic.

The Tory MSP says for months the SNP ignored the one million Scots who voted leave.

He says the SNP's policy on the EU is "as changeable as a Highlands summer day".

Mr Cameron says the Scottish government is guilty of "democratic changes a plenty" and "routinely flouting democracy", again citing the votes lost by the SNP in the chamber.

He says the SNP use Holyrood as a "fairweather friend to be used when required and ignored when convenient".

SNP MSP Ivan McKee says this is about giving the people of Scotland a choice. 

Mr McKee says the new UK government regime "lurches to the right".

The SNP MSP says the Scotland's Place in Europe paper gave prime minister Theresa May a "get out of jail free card" and she rejected it. 

He says the Tory prime minister has decided to shift the debate to an argument that she cannot win on time. 

"The current situation is not of our making and we have worked to find a compromise," he says. 

Here's some pictorial highlights from the debate, courtesy of the Scottish Parliament's photographer Andrew Cowan.

Image source, Andrew Cowan/Scottish Parliament

Image source, Andrew Cowan/Scottish Parliament

Image source, Andrew Cowan/Scottish Parliament

Image source, Andrew Cowan/Scottish Parliament

Labour MSP Alex Rowley says the debate must take part in a civil way and that parliament must set an example for the debate in communities.

Mr Rowley says the argument in Scotland has shifted significantly that in 2014. 

He says he has been consistent in saying that if the will of the people is for another independence referendum then there should be one.

"There is no will for another referendum," he says and "the Scottish people do not want another referendum at this time," he adds.

Could Scotland remain in the EU if there was a Yes vote?

Ms Sturgeon was asked directly if she backed full EU membership for Scotland, and she cited it as being "SNP policy". There has been debate over this point due to a number of SNP members backing Brexit, leading some to speculate that the party might not commit to full membership.

In any case, there is a distinction to be drawn between Scotland staying in the EU as the rest of the UK leaves, and it rejoining at a later date as an independent country.

Image source, Getty images

In 2012, the EU  said Scotland would have to reapply  for membership after leaving the UK, then a member state. Today, MEPs  still say Scotland would have to re-enter , but some important groups, such as the Spanish, have said they would not seek to "veto" Scotland becoming a member state.

Given the unprecedented nature of Brexit, this is another point there will be negotiation - and no doubt a row - over.

It is thought the SNP would look to use membership of the European Economic Area  as an initial "stepping stone"  towards full EU membership.