Cameron salts his porridge for Salmond

This blog's been gone too long. It's been such a busy month of politics that there's hardly been time to write a line that doesn't go to print - but that's an old excuse.

Whitehall goes to Holyrood today, albeit an empty Scottish Parliament where not even the public are allowed to tour the building while the MSPs are on holiday.

David Cameron is in town at the same time as I am - taking that first twirl on the dancefloor with Alex Salmond in this long elimination waltz to a referendum.

The two are meeting about now, while we all digest the contents of a very coherent speech from a British Prime Minister in defence of the UK.

Cameron spoke for the UK "head, heart and soul", as we had been briefed, but he may have over-extended himself by promising more devolution - if only the Scottish people reject outright the prospect of independence.

He refused to elaborate on what powers he might offer Holyrood, if the Scots choose to stay in the Union. Short of even more tax powers - the Scotland Bill will give the parliament power to raise a third of the taxes it spends - we're at a loss to see what he might mean.

Salmond has been quick to point out that this is an old Tory trick, promised by Sir Alex Douglas-Home a long time ago in the lead up to the 70s devolution referendum.

Without specifics it leaves Salmond facing an easy media goal this afternoon. But as the game is played out this "offer" of Cameron's may become more significant. Of course, it is not Cameron's offer at all, but that of George Osborne, the strategist who knows the Tories can't go into this referendum campaign simply saying No.

But back to the speech, which will be on the Downing Street website. It was far from the "threadbare" reasons for the UK that the SNP described it as.

Cameron began with humble pie, went on to condemn the Clearances (go tell 'em on Jura I whispered where his father-in-law has more deer than people on the island), and made the case for a fairer Britain.

There was a call to Labour arms - for Gordon Brown ,Alistair Darling, and John Reid to add their voices to the UK campaign - that didn't go unnoticed.

Strange to hear the case for social justice across the whole UK best articulated in Scotland by a Conservative Prime Minister. While the speech was good (hats off the former Guardian scribe turned Downing Street scriptwriter Julian Glover we're told) the human deliver mechanism - an Eton-educated, Conservative - might not be the best for Scottish ears.

Cameron acknowledged that in questioning, but his defence was that this, the Union, is what he believes in. With that vague vow on more powers Cameron may have slipped, or stepped on his partner's toe - the airwaves jury will decide. But, once again, Cameron shows he's not afraid to take the lead in this dance.