Thank goodness for University Challenge and the BBC! By disqualifying the clear winners - on an absurd technicality - a team that has won more public affection and generated more interest in medieval Latin and Mendeleev's periodic table than any other in the programme's history, the BBC has given the nation something less depressing to talk about than the credit crunch and Sir Fred Goodwin's pension.

With this self-harming decision, the BBC has confirmed its reputation for totally misunderstanding the public it is supposed to serve, but it has also performed a priceless national service by distracting the British people and the media from throwing tomatoes at pilloried bankers. More important, it has fulfilled its public service mission by pointing the way to a two-part solution for the global economic crisis and the credit crunch.

The first part involves some personnel changes that will surely appeal to anyone who has followed this week's events.

Sir Fred should immediately be invited to join the BBC's management, where he will find unstinting moral support and armour-plated bureaucratic cover for his insistence that rules are rules and contracts must always be adhered to, however unreasonable and unfair.

Gail Trimble, the brilliant and popular captain of the Corpus Christi College, Oxford, team, should be appointed Governor of the Bank of England, as she would instantly re-create the public trust demanded by this position, especially as the Bank embarks on an unprecedented experiment in printing money.

Finally Matthew Yeo, the captain of the accidentally victorious Manchester University team, should be brought into the Cabinet as Chancellor or, better still, as Prime Minister. Through his reluctant and self-deprecating acceptance of the disputed title, he has shown a keener understanding of ethics, diplomacy and the art of compromise than any politician in British public life.

Having settled these fine people into their new positions, the second step is to outline the policies they must follow to resolve the crisis - and in this respect, too, University Challenge can teach a lesson that Britain needs to learn. The key principle that people and politicians in Britain must understand if we are to emerge from the credit crunch is that the BBC and Sir Fred are dead wrong when they insist that the rules are the rules. On the contrary, rules have to be interpreted, changed and sometimes ignored.

Rules may be immutable in sports and board games, which was the principle that the BBC applied in the University Challenge case. But in the real worlds of politics, economics and social behaviour, rules, laws and contracts frequently have to be modified and reconsidered. Provided they occur in a fair, reasonable and transparent manner, such changes, are perfectly compatible with legal certainty and the rule of law. Indeed, flexibility in interpreting and changing regulations, is necessary for laws to be respected and observed.

What has all this to do with the credit crunch? If Gordon Brown had decided to play by the rules in the case of Northern Rock with the same rigour that the BBC applied to University Challenge or Sir Fred to his pension, savers would have lost everything above the £30,000 insured by the government guarantee scheme in force at the time. Similarly legalistic behaviour by governments around the world after the Lehman crisis would have meant depositors in every bank in Britain, America and Europe being wiped out.

Luckily politicians faced with the near-death experience of Lehman had the good sense first to ignore the rules and then to change them. As a result, bank deposits are now guaranteed in almost every country almost without limit.

The fascinating question is why nobody seems bothered that governments have offered savers this extraordinary retrospective largesse. Taxpayers had no legal obligation to guarantee uninsured savings. By offering these guarantees to savers, governments were deliberately repudiating the laws passed to make sure that large depositors in risky banks such as Northern Rock, Halifax and Citibank suffered if they went bust.

Why was there no public outcry about this sudden change in the rules, which resulted in a huge retrospective subsidy from taxpayers to savers?

The obvious answer is that everybody had some money in the banks. But this will not do, as small deposits were insured under the old rules anyway. It was only rich people, with more than £30,000 in deposits who stood to benefit, while all taxpayers would have paid for this generosity.

The real reason why governments tore up the rule books last year and won public support for doing so, was that everyone realised what was at stake - the loss of a single penny by any saver in any bank in any leading capitalist country would have triggered a run on every financial institution in the world and caused an economic catastrophe.

And here we come to the nub of the problem. Although the world may no longer be threatened by economic collapse, it faces a decade of depression unless the credit system can be revived. And the only way to revive the system is to offer vast public subsidies and support to the banks. Who owns the banks and whether bank shareholders or managers benefit unfairly from public subsidies are irrelevant.

Even if all the banks' shareholders were completely wiped out, nationalising the banks would still channel vast public subsidies unfairly to depositors and owners of bank bonds, who are probably much richer than the taxpayers on whose support they rely, and who could not have expected this support when they invested in the troubled banks.

Despite the apparent unfairness of retrospectively favouring some stakeholders in the banking system, at the taxpayer's expense, it is absolutely essential to give this support - the only alternative is decades of depression.

What politicians must now do is to persuade the public that the time for quibbling about the precise rules of bank rescues is over. Who cares whether the theoretical rules of corporate governance say that shareholders should lose everything before taxpayers pay a penny?

The banks must be given support - and if shareholders or managers gain unreasonably, such gains should be clawed back retrospectively, in a rough and ready way through special taxes or levies. The right criterion for bank rescues is the one that the BBC should have applied in the case of University Challenge: what is reasonable in today's conditions.

Reasonable is a wonderful English word with no commonly used equivalent in any other language. If Britain wants to save the economy and lead the world out of the present financial crisis, it must do whatever is reasonable to preserve the financial system - and do it quickly. The time to worry about getting the rules exactly right is after the crisis is over.

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