Are Scotland and England still diverging politically, in spite of all the hype?

There's a really interesting Twitter thread by David Clark, a former adviser to Robin Cook at the Foreign Office, in which he argues that the UK is still likely to break up within the next 10-20 years and that last Thursday's election result shows that beneath the headline story of a Labour victory, Scottish electoral trends are still diverging from the rest of the UK.  He points out that Labour has never increased its share of the vote at the end of a full term in power, and that therefore they are at risk of losing at the next election to the second-strongest electoral blocs, which in England is the right-wing vote for the Tories and Reform, and in Scotland is the pro-independence vote for the SNP and to a much lesser extent the Greens.

Obviously this is music to my ears, so I've been trying to work it through and see if it stacks up.  One obvious complication is that power in Scotland is not determined solely or even primarily by what happens in Westminster elections.  When the Holyrood election comes around in 2026, it won't be Labour trying to hold its vote at the end of a full term, it'll be the SNP trying to hold on after four full terms, which is a very different dynamic.  In a worst case scenario where the wheels really come off for the SNP, it might destroy their credibility as the main opposition to Labour in the run-up to the next Westminster election.

However, if the SNP can at least remain competitive in 2026, it's true that they would be extremely well placed to benefit from any Labour slippage in 2028 or 2029.  They are second in the vast majority of seats in Scotland.  I would question, though, how confident we can be that Labour will drop back, because although they may not have increased their vote share at the end of any previous full term, they certainly more or less held their ground in 2001 when Tony Blair was re-elected, and in Scotland their vote actually increased in 2010 after three consecutive terms in office - albeit that may have been partly down to a personal vote for Gordon Brown.  Luckily, in spite of the hype, there aren't many Scots at the beating heart of the new Labour government.