An argument put forward by some Labour types is that we're not really facing a debt crisis at all. "Yes, the national debt levels are bad," they say, "but we started off at a low level in comparison to other countries, so we can absorb the deficits we're racking up."
Well, you can take issue with the idea that we had "low levels" of debt before the crisis kicked in – but the real mistake this statement makes is to ignore the rate at which we've accumulated debt. As the latest OECD data shows, UK debt is set to rise faster than any other nation save for Iceland and Ireland:
The picture would probably look even worse if you accounted for all the off-balance sheet fiddles, like the toxic bank assets and PFI. And this is why the markets are worried: the UK's current debt levels are scary enough, but the trajectory we're on is absolutely terrifying. It wouldn't matter too much if they could be sure that the brakes are going to be firmly applied. But, alas, there's no sign that the current government are going to do that.