Why withdrawal of Rock guarantee matters
The government's decision to withdraw the guarantee that no saver in Northern Rock could lose even a penny if the bank went kaput has wide implications.
The least important is that the reconstructed nationalised bank - with the bad bits taken out - is well on the way to being privatised.
More important is what it means for the security of savings at other banks.
Because while Northern Rock's savers benefited from a formal guarantee from the government, the Treasury was also in effect promising that no saver in any British bank or building sociey risked losing a penny.
So in withdrawing the Rock guarantee, the chancellor is in effect restoring an element of caveat emptor to the entire banking market.
To be clear, the banks' insurance scheme - the Financial Services Compensation Scheme - provides cover up to £50,000 per customer.
But if you have more than that in a single bank, well that increment is at risk. You can lose money if your bank has insufficient assets to meet its liabilities.
How would you know whether your bank is prudently managed or not?
There's the rub. Millions of us wouldn't have a clue how to make that judgement.
But most of us instinctively - and correctly - know that some banks are too big and important to fail, that they would always be bailed out by government were they to run into difficulties.
So those banks have an unfair competitive advantage: they attract more funds and at a lower interest rates than the smaller banks and building societies that are less important to the economy and can't be sure that they would always be protected by the Treasury from falling over.
Which is why it matters so much that those too-big-to-fail banks (you know who they are) don't abuse the protection given to them by the state - by us, by taxpayers - to take excessive risks in pursuit of incremental profit and bonuses.