If 'not now' when will a second referendum take place?

Delegates at the SNP conference in Aberdeen are being told today Scotland will have another referendum.

The party faithful are being promised by the leadership that they will not be denied a vote on independence.

But is that a promise their leaders can keep?

The SNP firmly believe they have the moral authority to call another referendum. But it is the UK government who have the legal authority to decide when or if there is another referendum.

• Scotland 'will have its referendum', says SNP's Robertson

• Theresa May says "now is not the time" for fresh vote

• Sturgeon 'determined' to have second vote

• Indyref2: Your questions answered

So what are Nicola Sturgeon's options now?

I've just asked her what she will do if Theresa May refuses to discuss the possibility of another vote.

The First Minister says she is convinced the PM's position is not sustainable, that she cannot continue to deny Scotland a vote without incurring major political damage and possibly even strengthening the case for independence.

For the SNP this argument about who has the right to decide when or if Scotland can have another referendum is an example of why Scotland should leave the UK.

It allows them to make the case that Scotland is once more being dictated to by Westminster and says that shows why independence would be a better option.

Could a date be negotiated?

Just saying no might be a politically risky path for the Prime Minister but if she sticks to that position what can the Scottish government do?

They can demand negotiations over when a referendum could take place. But they can't enter discussions with someone who won't speak to them.

There is the option of holding a referendum without the authority from the UK government. That would have no legal standing and it could be challenged in the courts.

But it could also demonstrate the strength of feeling in Scotland.

Theresa May has said "now is not the time" for Nicola Sturgeon to call for an independence referendum

Ms Sturgeon will not yet discuss that possibility, saying she is concentrating on the vote in the Scottish Parliament next week and then making a formal request to Theresa May to give the authority for another vote.

Speaking to me today, Ms Sturgeon indicated she might be prepared to discuss the timing of another vote with Mrs May.

The Scottish government want a referendum between Autumn 2018 and Spring 2019.

It looks like they would be prepared to negotiate a different, later, date.

However, it is not yet clear that the UK government are prepared to talk about a date.

The PM did say "now is not the time" for another referendum. She didn't say never. So, will she talk about holding a vote in the future?

That seems to be the question today.