Agence France-Presse: BP chief executive Tony Hayward blamed Wednesday an unprecedented series of failures for the Gulf of Mexico oil spill and said he was “personally devastated” by the catastrophe. “I understand people want a simple answer about why this happened and who is to blame,” Hayward said in testimony prepared for delivery in his first appearance Thursday before angry US lawmakers. “The truth, however, is that this is a complex accident, caused by an unprecedented combination of failures. …