document: Early this morning, Nicola Sturgeon announced she would be giving an "important speech" today in the grand surroundings of Bute House, her official residence.
  Among SNP sources, the chatter was that she would give an ultimatum to Theresa May that if she could not negotiate a differentiated Brexit deal for Scotland she would push for a second independence referendum.
  Forget that. Scotland's first minister has gone the whole hog, saying she will next week push the button on a second independence referendum by putting legislation to the Scottish Parliament.
  Sturgeon can probably win that in Holyrood, but can she win the referendum?
  Her announcement will delight her many many supporters.
  She is undoubtedly a hugely effective and talented politician. During the last referendum, the SNP's support grew very significantly and they managed to enthuse many thousands of new members to their cause.
  But does the SNP have an updated economic argument? Is she willing to risk rancour from many Scottish voters who want another referendum like a hole in the head?
  As I've written before, the UK and Holyrood governments are set for a battle royal over timing of a potential vote.
  But the question first is whether or not the prime minister is willing to grant a vote. Under the law, Westminster has to grant the referendum; it's not just down to the Scottish government.
  I'm told Number 10 had carefully worked out "countermoves" depending on what the first minister's message was this week.
  Now Sturgeon has made the first big move, it's down to the other side to respond.
  But arguably we have just entered into the most complicated, most fraught, most fundamental period of political uncertainty for our country in a very long time.
  Sturgeon's announcement confirms that it is not just our place in the EU that is changing, but the relationships between our own nations that are at question too.
summary: Before the Parliamentary drama over the first part of Brexit is even done, another dramatic twist in this most tangled of plots.