There are several heresies in the investment business that can harm you if you believe them. One is astrology. Probably almost no Financial Times reader will be troubled by that one, but you would be surprised how many readers of fashion magazines and the like give it attention.

Another is “technical analysis” – the idea that by studying the shape of the market’s wiggly lines you can predict the future. Famous “swamis” have arisen, such as Joe Granville and James Dines whose pronouncements would move markets. Yet it has been only a matter of time before they crash and burn.