BP PLC came within 3.55cm of preventing the worst offshore oil spill in US history, say engineers studying the safety device that failed...In a report released yesterday, engineers say the device failed because the force of the blowout bent the drill pipe, knocking it off-centre and jamming the shears...Investigators concluded the blowout preventer failed as a result of a design flaw, not because of misuse by BP or any other company involved, and not because of poor maintenance. The failsafe device wasn't designed to handle a real-world blowout..."They have to rethink the whole design," said Elmer P. Danenberger, former overseer of US offshore drilling rules.