The prospect of BP being found guilty of gross negligence over last year's oil spill in the Gulf of Mexico appeared to recede yesterday when its main partner operating the offending Macondo oil well agreed to drop all claims against it as part of a $4bn (£2.5bn) out-of-court settlement. Anadarko Petroleum's payment ends a long-running row between the two about liability for the accident that claimed 11 lives. Each will drop all allegations against the other. The explosion on the BP drilling unit Deepwater Horizon devastated wildlife along the US Gulf Coast. As a 25 per cent shareholder in Macondo, Anadarko could have been liable for a quarter of the total cost of cleaning the spill, unless it persuaded a court BP that was grossly negligent.