“Small oils” are showing again why they provide one of the great white-knuckle rides for investors and managers. There are times, for certain companies, when every dry hole drilled halves the share price. That is what happened this week to the stock of BowLeven, a small UK-based oil company, after it reported a dry hole off Cameroon, and what happened last October when the same company revealed a similar abortive drilling in the west African state. So investors have seen their original stake at BowLeven’s flotation 13 months ago on London’s Alternative Investment Market first doubled and then halved. Choosing red or black in a casino might seem an equally rational bet.

“But BowLeven is not the first to go flying up and come crashing down, and won’t be the last,” says Richard Slape of Seymour Pierce brokers. Among other Aim-listed companies that have fallen to earth in the past year are Regal Petroleum, which failed to find oil in Greece, the aptly named Wham Energy whose first well in the North Sea proved unproductive, and First Calgary, the Canadian oil company that was once Aim’s biggest stock. Aims’s worst performers are the newest comers. Of 29 companies that listed last year, only 41 per cent have shares trading above their issue price, according to Mr Slape. This reflects the higher expectations of poorer quality companies that are typical of today’s maturing oil boom.