To see how trend-followers aren’t all about rocket science, take one of the forefathers of today’s fund managers: Chicago-based trader Richard Dennis. In the 1980s, he made a bet with a rival that successful traders could be taught, that it wasn’t an innate talent. As part of the contest, Dennis taught a breed of traders he called ‘Turtles’ because he trained them to lock into specific market trends and ride them, just as turtles ride sea currents. What was important was to decide on a system and stick with it. The approach lends itself to computerized dealing, because in it, trades are often triggered by the dynamics of the market itself. A classic example is the moving average. Track the five-day moving average of a stock and, some traders believe, you should buy where it crosses above the 30-day average or sell when it falls below. Such ideas can be converted into an algorithm that tells a computer when and how to trade. The turtles’ edge, like trend-followers today, was in exploiting the reality that mainstream economic theory doesn’t allow for: financial markets don’t behave efficiently, but follow vogues and panics. “The overwhelming fact is that this thing that shouldn’t have worked has worked for 30 years,” said Harding over lunch at his local West London Italian restaurant. Computers don’t need to be persuaded to hold firm when the market turns against them.