Alistair Darling insisted many times yesterday that the decision to nationalise Northern Rock reflected a desire to "safeguard taxpayers' money". The chancellor was clear that the private sector bids on offer involved large subsidies with little upside for the government if the bank's fortunes improved.

At worst, taxpayers could lose about £100bn or 7 per cent of national income. But this disastrous outcome is so unlikely, that it is not really worth considering.