The trait, associated with higher exposure to testosterone in the womb, has been linked to confidence, risk-taking ability, extra vigilance and quick reactions. Not only did traders with long ring fingers make on average six times more money, they survived more years in a cut-throat world.

All 44 men in the study, some of whom made £4m a year, worked in the City of London, buying and selling securities worth billions but holding their positions for only minutes or even seconds. The Cambridge University scientists, led by Dr John Coates, himself a former Wall Street broker, compared the profits of the traders over a period of 20 months with their finger-length.

Traders with long ring fingers made up to 11 times the earnings of their counterparts. On average they made six times as much, and the length of their ring finger was as influential as their experience.  The research mirrored previous studies which link finger ratios with performance in competitive sports such as football, rugby, basketball and skiing.

Dr Coates, reporting in the journal Proceedings of the National Academy of Sciences, said: "We were surprised to find that exposure to hormones in the womb had such a strong influence on future trading performance. But we should not conclude from this that only people with long ring fingers should be employed in the stock market. That is a bit like only training tennis players who are tall. It may be advantageous for their serve but that would exclude such players as John McEnroe and Jimmy Connors."

So... another way of identifying them apart from the smugness and arrogance.

Sometimes it was just a little more obvious...

The original was here