Near the beginning Fred Thursday and Dorothea Frazil are on a bridge with a white house in the background. On it is a large digital TV aerial at a time when most people still had black & white sets let alone colour. Digital TV did not appear in the UK for another 30+ years.
When the old guy is found dead in his narrowboat, and the murdered woman's purse recovered from it, this is reported to have been at Gas Street Basin. This is right in the heart of the City of Birmingham, surrounded by tall buildings. But it is depicted as being in a totally rural setting.
Chief Superintendent Reginald Bright is still listed in credits as CS, but is wearing insignia of Assistant Chief Constable the next higher rank.