Guardian: Shares in BP plunged 7% today as investors panicked about speculation that the blowout on a rig in the Gulf of Mexico could create an even bigger environmental disaster than the Exxon Valdez tanker spill. Fund managers and analysts in the City said they were deeply worried about the financial cost to BP of the kind of legal action that could be taken in the US by those damaged by the accident. Over £13bn has so far been knocked off the oil company’s stock market value since the …