Guardian: We thought it was big, but now we know it is huge – the greatest accidental oil spill in all history. The latest calculations of the vast quantity of oil polluting the Gulf of Mexico after the blowout of BP’s Macondo well conclude that 4.9m barrels poured into the ocean. The scientists making the estimate believe it is accurate to within 10%, so even the smallest leak would be a third bigger than the 3.3m barrels released into Mexico’s Bay of Campeche when the Ixtoc I oil rig blew out in …