Doctor Death: Britain's Worst Serial Killer (True Crime Documentary) Britain’s biggest serial killer was a doctor, Dr Harold Shipman. Unsuspected for many years, Dr. Shipman selected his victims from his patient list. There were clues, but who in the community would believe that a doctor would kill his patients? Suspected of killing over 350 people during his career, it was clumsy attempts at forging the will of one of his victims in his own favour that alerted the police and led to his arrest. Found guilty at his trial and jailed for life, Dr Shipman committed suicide never accepting his guilt.