In a bid to seize the initiative back from the UK government, the SNP has just announced autumn 2014 - a few weeks after the 700th anniversary of Bannockburn - as its preferred date for a referendum on Scottish independence. Nicola Sturgeon, the party's deputy leader, broke the news a few minutes ago on Twitter.
This would be an advisory referendum (the Scottish government does not have the legal right to hold a binding referendum) designed to provide the SNP with a clear mandate to negotiate for independence. But in his statement to the Commons earlier this afternoon, the Secretary of State for Scotland, Michael Moore, denied that Alex Salmond's administration even had the right to hold this. Westminster insists that it must determine both the timing and the wording of any vote. The course is set for a dramatic constitutional collision.