Most episodes are believed lost, with just 10 of the 39 known to survive. The first six consecutive editions exist, though whilst all were made on colour videotape, the opening five are only 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.
A voice-over on the closing credits informed viewers of the first run that "Ewan Hooper is director of the Greenwich Theatre." The actor had been a key component of the Croom's Hill theatre's revitalisation in 1969.