Most episodes are believed lost, with only 10 of the 39 known to survive. Though all were made on colour videotape, the opening five only survive as monochrome 16mm film prints.
Creator Ted Willis (who had earlier devised Dixon of Dock Green (1955) for the BBC) did his research by chatting to the local police force of the North Northamptonshire town of Rushden, the series' filming location for the fictional Broadstone.