You have just invested £1,600 in assorted British banks - if you are an average income taxpayer, that is. Chancellor Alistair Darling has done it for you.

Another calculation is that the £50 billion he is stumping up as new capital for the banks is equivalent to £2,000 for every British household.

On top of that, he is offering to guarantee money that British banks borrow in the markets to replace loans they are due to repay. Mr Darling expects the banks to take up some £250 billion of this Government-guaranteed cash. That would put £10,000 per household on the line.

Be thankful that you do not live in Ireland where the Government’s guarantee covering all deposits in the country’s banks is equivalent to £77,000 per person.

That is one reason why Mr Darling dodged every demand that he should make a similar guarantee here. Instead, he repeated the mantra that he will “do what it takes” to look after people with money in banks that crash, starting with the Icelandic Icesave.

What you will get for your money you may not discover for some years. This is a very long term investment, but with one very short term objective - to get the banking system working again and to put a stop to the recurrent rumours that this British bank or that is heading for the rocks.

Contrary to leaks on Tuesday, the Chancellor stopped well short of nationalising any banks. For a start, his scheme is voluntary. HSBC, Britain’s biggest bank, said it will not be using it. So did Standard Chartered and Spanish-owned Abbey. Nationwide building society was undecided.

The pressure point is that banks which wish to use the £250 billion guarantee, must accept a Government investment and the strings that come with it.

The Treasury left these vague. There was no hint of the Government appointing directors to bank boards, nor even demanding the removal of incompetents and rogues who have trousered seven-figure bonuses for steering the banks they run into their present plight.

It will just set unspecified rules about fat cat bonuses, dividends for shareholders (other than the Government) and “require a full commitment to support lending to small businesses and home buyers”.

The Treasury will also seek to get a decent return from your money it invests in the banks, as well as fees for its guarantees. In theory could one day take you out with a profit.

However, the stock market’s reaction was brutal. In half-ordinary times the half-point interest rates cut from the Bank of England would have given shares a healthy fillip.

The opposite happened. Bank shares which had been ravaged on Tuesday by talk that the Chancellor would nationalise them, headed on down on news that he had settled for a halfway house.

Mining and oil shares were tumbling, too, because of the fall in oil and metal prices that persuaded the Bank that inflation is no longer the menace it was so that it could cut its rate.

On the face of it, the snap judgment was that the Darling plan and the interest cut that accompanied it was too little too late. Wall Street has passed the same verdict on the even bigger and less ingenious scheme whereby the US Government is paying American banks £400 billion to take dud loans off their hands.

The test, though, is not what the stock market does, but what the banks do. On Wednesday, several of them trimmed their mortgage rates almost instantly. An encouraging sign. If they now start approving mortgages in reasonable numbers again, it could steady the housing market quite quickly.

That does not mean going back to lending 100 per cent mortgages to people who cannot afford them, just providing enough home loans on tolerable terms to make ordinary homes saleable at ordinary prices.

Unlike the US, we do not have a huge stock of unsold and unwanted new homes that have to be shifted, or bull-dozed, before the market can come back to life. British house-builders wisely scaled back their activities as the mortgage famine developed.

It is only quite recently that small and medium-sized businesses began to complain that banks were cutting back their credit facilities or making the terms so tough that it was better to hunker down and not borrow money.

A sharp prod from the Treasury to those banks that accept your £50 billion could make a welcome difference.

In the end, though, none of it will do much good unless this avalanche of public money and Government guarantees persuades banks - round the world, not just in Britain - that they can lend to each other without the outfit at the other end of the deal going bust.

Confidence, not cash, is the currency that counts in this situation. It is still singularly lacking in the stock market.