Scottish devolution continues to place strains on politics at Westminster, writes Frank Millar, London Editor
Might the United Kingdom really be on a fast track to disintegration? This is not some flight of fancy born only of the continuing ability of Alex Salmond, leader of the ruling Scottish Nationalists, to set the agenda on behalf of his minority administration in Edinburgh.
The question might also appear an odd one to land at the door of Conservative leader David Cameron, following his passionate defence of the UK on Monday. Yet there are serious doubts about the ability of any future Conservative government, acting alone and no matter how well-intentioned, to resolve the perceived anomalies arising from the consequences of powers having been devolved from Westminster to the new Scottish parliament at Holyrood in Edinburgh.
The so-called West Lothian Question - whether it is right for Scottish MPs sitting in Westminster to vote on issues affecting England while English MPs are unable to vote on the same issues in respect of Scotland - is certainly being asked with renewed urgency.
However, even some senior Tories fear Cameron's answer - English votes on English laws - can only spread "the ugly stain of separatism" he now detects "seeping through the Union flag".
In Edinburgh, Cameron advised Salmond to "think again" if gleefully anticipating the election of a Conservative government.
"We will not play your game to break up our United Kingdom," he told the Scottish Nationalist Party leader: "And we will not stop fighting to meet Scotland's needs."
Intriguingly, Cameron also declared: "If it ever came to a choice between constitutional perfection and the preservation of our nation, I choose our United Kingdom. Better an imperfect union than a broken one. Better an imperfect union than a perfect divorce."
The former Ulster Unionist leader, now Conservative peer, Lord Trimble - who apparently enjoys reasonable prospects of a job in any Cameron administration - has cautioned that this policy would spell the end of Westminster as "the one sovereign parliament for all the UK".
Although Trimble also acknowledges an inevitable Northern Ireland interest in a debate that cannot be confined to England, Scotland and Wales, there is little evidence so far of engagement by the DUP, whose nine MPs missed the recent state opening of parliament.
None witnessed the exchange during the opening debate on the Queen's Speech in which prime minister Gordon Brown made the simple but still telling observation that just one-third of Scottish voters had actually backed the separatist party.
Based on opinion polls, the overall impression remains that Salmond's popularity continues to rise, even as support for Scottish independence has slightly fallen back.
This is not to say the unionist parties should content themselves Scots will be forever happy to settle for the luxury of an "opposition" administration in Holyrood while clinging to the security of a Labour government in London.
Since breaking Labour's grip in the parliamentary elections last May, Salmond, as first minister, has shown himself head and shoulders above his political competitors.
Limited by the absence of an overall majority in Holyrood, Salmond nevertheless talks the talk in a way that not only exudes self-belief, but also seems to generate greater public confidence that devolution should at least be a "process" rather than "an event".
Indeed, although they would deny it, the first minister can claim to have already forced the Scottish unionist parties radically to alter their attitude to the devolution of greater powers in response to his call for a "national conversation" about independence, something Salmond accepts is at least 10 years away. There will be at least two UK general elections in that time.
Some informed sources say Cameron is well disposed to Northern Ireland and would love to see a centre-right party offering a real political alternative there at some point in the future.
Sceptics suggest the Tory leader's interest extends only to the fact that he might need nine, 10 or 11 DUP votes in a tight parliament. East Antrim MP Sammy Wilson has already warned that Cameron won't get them if he persists in creating "two classes of MP" at Westminster.
Wilson also notes, with some logic, that the question of a Conservative/DUP deal might hardly arise if the putative Conservative prime minister intends to deny them the right to vote on "English-only" issues.
This should weigh with Cameron. The imbalances in Britain's electoral system still suggest it will be difficult for the Conservatives to win a secure majority in one go. A "hung parliament" remains a distinct possibility, and even Wilson accepts that the Tories should see the DUP as natural allies.
So an interesting tension might lie in prospect between Cameron's answer to the so-called West Lothian Question and his possible need of unionist support in the next House of Commons. However, some traditional Conservative and unionist supporters in London believe that if Cameron really wants to save the Union, the issue cannot be left to the next election.
Informing this view is a recognition that a Conservative government mandated by English votes would find it extremely difficult to resolve constitutional, financial or political grievances arising from devolution without inflaming nationalist sentiment in Scotland.
Last week, the Scottish Conservatives acknowledged the reality of their reduced position, coalescing with Labour and the Liberal Democrats to secure a constitutional commission to rival Salmond's "national conversation".