Martyn Pritchard, a hippy, drug squad detective, based in Oxford, lived and worked undercover for 5 1/2 years, during the 1970s. A young warden was cultivating a plot of cannabis plants in the Lions' Reserve at Longleat Safari Park in Wiltshire. This became an inquiry for the detective and a potential story for a Mirror reporter, which is how the author and detective met. Together they became entrenched in the biggest drugs scandal Britain has ever known.