The way in which oil is traded on commodities markets is coming under close scrutiny. Last month, officers of the European Commission raided the London offices of BP and Shell along with Norway's Statoil company and the leading price reporting agency Platts. They said they were investigating claims of collusion to manipulate the prices of oil and biofuels on the international markets. A leading city insider tells File On 4 that the price-reporting mechanism for oil is 'wide open to abuse' So are petrol prices being kept artificially high by hidden forces beyond the normal workings of supply and demand ? Gerry Northam investigates and asks whether British regulators are proving slow to recognise the potential problem. Producer: David Lewis.