GE2019: Scotland heads into uncharted constitutional waters

• ITV Border's Political Editor, Peter MacMahon: his take on the election results.

This is a stunning victory for Nicola Sturgeon and the SNP, with the nationalists making sweeping gains across Scotland.

It was always clear that the SNP was going to do well in this election, but this result has exceeded even the expectations of senior, and experienced, nationalists. Indeed of the First Minister herself.

Three seats across the ITV Border region in the south of Scotland are among the few the Tories have managed to retain.

Scottish Secretary Alister Jack kept his Dumfries and Galloway seat, beating off a strong challenge from the SNP's Richard Arkless, who won it in 2015 but lost in 2017.

John Lamont retained his Berwickshire, Roxburgh and Selkirk seat against another strong SNP candidate and former MP, Calum Kerr.

And former Scottish Secretary David Mundell kept his Dumfriesshire, Clydesdale and Tweeddale constituency against the SNP's Amanda Burgauer, another well-respected opponent.

So the thick Tory blue line north of the Border that goes from Portpatrick in the West to Eyemouth in the East remains, even if the majorities that delivered it are much thinner.

What is also clear from this election is that Scotland and England are diverging politically. The Scots - in general - appear not to have warmed to Boris Johnson and his brand of Conservatism.

And, again to generalise, they seem to prefer the kind of politics which is put forward by Ms Sturgeon and the SNP, who are in power in Holyrood.

We will have to wait for the final results, and further research into them, to determine whether the SNP's opposition to Brexit or its support for a second independence referendum was the key factor.

Or whether it might just be that this time around more independence supporters came out for the SNP, even if the Tory vote was not wiped out.

Or whether some electors, Labour or former Labour voters, 'lent' the SNP their vote to try to do what the First Minister said were two of her objectives: stopping Brexit and keeping Boris Johnson out of Downing Street.

Whatever the reason, and it could well be some mixture of all of them, this result will massively strengthen the SNP's demand for a second independence referendum.

Ms Sturgeon will call for one, and if he sticks to his campaign pledge, Boris Johnson, back in No 10, will say 'No'.

Given that the power over the constitution resides at Westminster it is hard to know what will happen next. Ms Sturgeon was asked this morning what she would do if the PM did say 'No' and she would not be drawn.

She did accept that Mr Johnson now has a mandate "to take England out of the European Union" but she added she had mandate for Scotland to choose its future - by which she means having a referendum on independence.

Beyond that, and accepting not everyone will support independence, Ms Sturgeon tried to turn the question back on Mr Johnson and the Tories - what would they do now she had her mandate?

But despite being in a very strong position following this election, the First Minister will have, at some point, to have an answer. We know the SNP and the Greens will support indyref2 in Holyrood legislation, before Christmas, but if the PM says Westminster will not give consent, then it's back to Ms Sturgeon.

Where this will all end, it is impossible to say. Nothing Nicola Sturgeon has ever said suggests that the First Minister would go down the 'Catalan road' of holding a referendum which is not legal.

She may hope that this election result will simply increase the pressure on Mr Jonson and his party to a level that the new UK Tory government cannot deny indyref2. But that is highly unlikely.

It is therefore possible that the debate will continue, and indeed intensify, in the run up to the 2021 Holyrood election.

So, Mr Johnson can claim a great personal victory being able to 'resolve' one constitutional issue, Brexit - though there will be long negotiations on the details of that to come.

However, by moving substantially forward on - if not concluding - one massive constitutional issue, Brexit, he will plunge the country into another one - over the future of Scotland.

If the Prime Minister refuses consent, as we expect he will, and Ms Sturgeon maintains her demands, as we know she will, then the good ship Scotland is sailing at a rate of knots into storm-tossed uncharted constitutional waters.