When Roy Herridge retired from the Metropolitan Police in 1991 he possessed the most commendations for police work ever awarded to a UK police officer. The cases he handled included the Ealing vicarage rape, the starving to death of four-year-old Heidi Koseda, the first black supergrass (Errol Walker), and Operation Shampoo - a drugs-ring case from which Herridge was ordered to withdraw and about which he still feels bitter. This account of his experiences in the force shows not only the nuts and bolts of detective work, but also the use of new techniques such as DNA fingerprinting and psychological profiling.