PM Theresa May comes out fighting for United Kingdom

Theresa May came to Glasgow with a clear message for Nicola Sturgeon and the SNP - stop obsessing about independence and concentrate instead on governing Scotland.

She accused the SNP of "tunnel vision" about the constitution. Saying "the SNP play politics as if it is a game" and accusing them of neglecting devolved public services like schools.

It is not hard to see why the Prime Minster wants to stop the talk of another referendum on Scottish independence.

The last thing she needs is to be fighting another referendum campaign whilst also trying to negotiate the UK's exit from the EU. Even though the assembled Conservatives at the conference here today insist they would easily win another referendum.

• PM Theresa May makes case for 'our precious Union'

The Prime Minister knows she could easily prevent another referendum by simply refusing to allow it.

The Scottish government has to ask the UK government to devolve the power to hold another vote before it can go ahead. That's how it worked in 2014 and how it would have to work again.

Mrs May won't currently answer questions about whether she would block indyref2, as it will inevitably come to be known.

Scottish Conservative leader Ruth Davidson applauds Theresa May alongside her party colleagues

At the moment she says she will not answer hypothetical questions. But it's possible that fairly soon this may be a very real dilemma.

She says there is no need for another vote, but she knows that if she refused to allow a referendum that could provoke a constitutional crisis that could generate support for independence amongst Scottish voters.

Nicola Sturgeon says there is another way the PM could avoid indyref2. She could agree to the Scottish government's proposals that advocate Scotland remaining in the EU single market.

But nothing that Theresa May said today suggests she will agree to to that.

Dress rehearsal for what will come?

UK government ministers say that everyone is eager to secure the greatest possible access to the single market but that there will be no separate, bespoke deal for Scotland.

So will there be another indyref? Very possibly.

With all the talk of another vote being "very likely" and "all but inevitable", Nicola Sturgeon has already marched her troops so far up the hill it's hard to see how she can march them back down again without massive loss of face and political capital.

Today we got an extensive preview of the unionist case.

Mrs May talked at length about the benefits being part of the United Kingdom has bestowed on Scotland and the rest of the UK. And warned of the economic dangers of independence.

It was a serious and substantial speech about why she believes the UK is "Better Together".

If there is to be another referendum you can expect to hear these arguments repeated again and again. This may have been a dress rehearsal for the campaign to come.