Mr Darling knows that to establish credibility as an independent Chancellor, he will have to resist signing some of the Prime Minister's blank cheques. He must set out how, having let spending rip to shore up a wobbling economy, the Treasury intends to restore sanity to public finances. If there are to be tax cuts, here's an opportunity to fund them responsibly, through reductions in a Budget that became grotesquely bloated under the bloke next door.