Does anyone in London actually know how the Barnett Formula works?

We’ve just had two years of intensive constitutional politics. Time enough, you’d think, for even London-based politicians and commentators to work out how British politics actually works. But if you think that you’d be wrong. Very wrong.

Consider our old friend the Barnett Formula. Antiquated and not entirely fit for purpose – it being a 1970s convenience that was itself an updated version of the 1880s Goschen Formula – but hardly a mystery or a terribly complicated piece of financial wizardry. And yet it seems that almost no-one in the Westminster village actually understands how Barnett works.

Yesterday, you see, Jim Murphy promised that he would use Scotland’s share of the proceeds from Labour’s so-called Mansion Tax to hire an extra 1,000 nurses north of the Border. Actually, daftly, he promised to hire 1,000 more nurses than any number of nurses hired by the SNP. If the SNP were to promise 5,000 Labour would promise 6,000 even if there was no need for that many nurses.