Thanks to Budget purdah, we’re all in the dark about what will be in George Osborne’s Red Book today. Oh, sorry, that’s wrong, don’t know what I was thinking. Truth is that, unless the Chancellor has some monumental surprises lined up, we’ve actually heard about much of the Budget in advance. We know, for instance, not just that he’ll cut the top rate of tax from 50p to 45p, but also — courtesy of Andrew Grice in the Independent today — the internal political slog by which he reached that decision. Thanks to the proclivities of coalition government, this has to be one of the most pre-briefed Budgets ever. There