In the United Kingdom, there exists a paramilitary unit called Group 13

One individual – a former civilian undercover agent for the security services, recounted his story of a encounter with Group 13.  Gary Murray, author of “Enemies of the State” had decided to research Group 13 to write a book on them.  He soon changed his mind.  One day during his research phase he was forcibly dragged in to the back of a Transit van and had a gun stuck to his head.  A voice told him it would be unwise to continue his project.  Sensibly, he decided to abandon the project and instead write a book on an altogether different subject.