Few signs that the stock market is in trouble are as reliable as surging unit trust sales.

Most individual investors in unit trusts are cautious souls in search of cream to top up their company pensions. They can rarely be tempted in at the bottom, especially given that the trough in equities is so often accompanied by comfortingly high interest rates chez the building society.

Only when rates fall and equities, fuelled by cheap money, head for the heights can they be tempted to buy. By which time, of course, the market is usually on the turn.

This cycle is no exception. Seemingly oblivious to the way the stock market has lost 15 per cent since its February peak, and to the unnerving volatility that has had shares yo-yoing at every turn, private investors are dutifully piling in.

The rush to buy PEPs before the end of the tax year made March the best month ever for unit trust sales. But even without an artificial boost, April still managed to be the best April on record. Not, though, that this surge was fuelled by the professionals - almost three-quarters of net buyers were private individuals compared with 50 per cent a year ago.

The industry's explanation of this seemingly perverse behaviour is simple; unit trust investors are buying for the long term, and are unperturbed by short-term market trends.

But closer to the truth is likely to be the fact that, deprived of privatisations, and with building society rates so poor, private investors cannot find anywhere more exciting to leave their money.

They should think again. Even for long-term investors, timing matters. There is little point in buying on the way down if you can avoid it. Opinion is divided over how much further the stock market has to fall. But the consensus is that we have not yet hit bottom. Investors should seek out the best-paying deposit account they can find, and sit tight until the autumn.