This is a high quality, well written series which contains excellent acting and believable plots (well, more believable than "Midsomer Murders" for example). The episodes can be viewed as standard "whodunnits" but also spectacularly reveal the massive changes in law, attitudes and culture in the UK over the past 45 years or so.
My only gripe is that, despite the great attention that is paid to period detail, the writers always make the mistake (not restricted to this series) of scripting the words "against you" in the caution used by a police officer when making an arrest. The UK police caution in such circumstances before 1995 was: "You are not obliged to say anything unless you wish to do so but anything you do say may be given in evidence." The words "used against you" were only ever used in USA. To have used these words in UK could have prejudiced the case.
My only gripe is that, despite the great attention that is paid to period detail, the writers always make the mistake (not restricted to this series) of scripting the words "against you" in the caution used by a police officer when making an arrest. The UK police caution in such circumstances before 1995 was: "You are not obliged to say anything unless you wish to do so but anything you do say may be given in evidence." The words "used against you" were only ever used in USA. To have used these words in UK could have prejudiced the case.