SNP prepares to cross the nuclear line in Perth

To Perth for the last, the very last, conference of the season - the SNP.

It was only walking past the boarded-up Perth City Hall this morning that I remembered the first time I came to the city was to heckle Margaret Thatcher at the Scottish Conservative Conference way back in 1980shomething.

These were different days - the Tories were still a force in Scotland, and dominated UK politics. The SNP was a rump vote and the Labour Party,  yes the Labour party,  was anti-EU and had a  unilateralist defence policy.

The dubbing of 1983 forced Labour to cross that anti-nuclear rubicon which the SNP looks set to do today when it votes to reverse its opposition to NATO membership.

The party will remain anti-nuclear and that isn't really compatible with NATO membership rules as George Robertson, former NATO Secretary General, loves to remind them.

Nonetheless the SNP anti-nuclear campaigners think it is compromise too far but they look to be outnumbered by activists who will maintain the discipline and the focus on trying to win a referendum. It doesn't look like it will come to blows but expect a lively debate.

For the leadership, for Angus Robertson in particular, the shift is all about having a more coherent defence policy, although NATO or not, that is under considerable fire from the UK government this week. (See the MoD document on defence implications for an independent Scotland here )

Practically, on the ground, I'm not sure what the policy change will achieve. It feeds into the calm the horses, nothing will change, message of assurance that Salmond wants to send to the Scottish public. I'm not sure if it will swing that many voters to independence. But it costs the party activists on the ground, when you could argue it needs them most, and it creates unnecessary division in the party where previously non existed. No price to large for the final prize.

Speaking of prices, the SNP leaderships seems keen ot prove the  old propagandist's maxim that if you repeat something often enough it will be accepted as the truth.

The one stat that's been trundled out by speaker after speaker in the last two days is that Scotland contributes 9.6 per cent of UK taxes but receives only 9.3 per cent in return. John Swinney did it again this morning and he should know better.

It's not really an apples and apples comparison. In numerical terms that's £53.1bn in to the Treasury pot and £63.8bn back out, as spending is higher than the tax take, thanks to borrowing.

Similary the "Independence Dividend" of £500 for every man, woman and child  that Nicola Sturgeon and Alex Salmond trumpeted yesterday is based on  one year, 2010-11, when Scotland's levels of indebtedness was lower than the rest of the UK.

The "Indy Divi" - and I loved The Sun turned it into a giveaway promotion "Free Offer" -  is just £500 less debt in one year, not £500 in your hand. Plenty more of that "nonsense" before the music ends in 2014.