There is a lot to admire about this series if you can accept the dramatic aesthetic identical to that of the graphic novel or 'co-mix', both visually and in terms of narrative structure and presentation. This style is becoming almost standard for 'action' films or thrillers these days, whether made for the cinema or for TV. It is certainly how most of these dramas come across, and I have to admit that I usually have a problem with this fast moving style, which is frequently dependent on sensational video editing, gruesome violence, and narrative short cuts or sleight of hand. But taking the series as a whole, it is perhaps the best justification for the co-mix style I have yet come across when taken to this kind of extreme where each story has to fit neatly inside an hour. I won't try to describe what sort of series this is in general since this has been well covered by the other reviewers of the two separate seasons here on Amazon and it would be tedious. My own special interest is in the attempt to achieve a dramatically useful and fairly convincing form of period dialogue which distinguishes itself from the usual embarrassingly flat late 20th century dialogue which is all that we normally get from historical dramas (e.g. the Ken Folett historical 'epics' such as The Pillars Of the Earth and its sequel World Without End, or the over-praised Game of Thrones). For this reason, in recent years, I've taken an interest in, and been very impressed by, the period dialogue of 'Deadwood' and 'Garrow's Law'. As far as I know there has been very little said anywhere about the sort of dialogue one tends to find in 'graphic novels', co-mixes or, if you insist, comics. I have noticed that this dialogue is as singular as everything else about this genre and that in certain cases which interest me you could describe it as stilted and even pretentious by ordinary standards. But every genre deserves to be judged to a certain extent in its own terms and in this graphic medium the language does not jar in the same way it might arguably do elsewhere. I have very little interest in this medium myself but that is due more to either (1)the content or subject matter, or (2)the style of so much of the draftsmanship, than to the medium itself. I see no reason why the graphic novel couldn't have become a real art form - although in my view it hasn't - but it's obviously what we call a 'popular art form'.
In respect of language two of the episodes, 'The weight Of One Man's Heart' and 'Threads Of Silk and Gold', one from each series, were even more interesting than any of the others which may have had different writers. I can well see that it was the kind of writing likely to make the average critic respond with the predictable cliche about lines that no actor could speak convincingly and to point to the actors looking uncomfortable to prove his point. But what may escape most viewers is that when the language is working well it amounts to a kind of verse drama. Admittedly there is something of an experiment about it all but I'd say it's well worth doing, and of course people might well look like this when choosing their words carefully and trying deliberately to distance themselves in a class-conscious Victorian way from the brutal events and squalid milieu of such story lines. It's not just a matter of period dialogue for its own sake, nor is it a matter of its historical accuracy. It's more a matter of the dramatic effectiveness of a heightened and more dramatic dialogue which earlier, and yes, often more educated, forms of speech make possible. Above all it's intelligent and goes a long way towards convincing you that the 'graphic novel style' that we have here is also intelligent in some way - as for example the recent BBC serial 'Hunted', or 'Dr Who' and now 'Musketeers' (all in the 'graphic novel style) DO NOT. That is one reason why this kind of dialogue offers such opportunities to the writer. It allows the writer to make the characters more articulate and therefore more conscious of the issues which are driving the drama. The two episodes mentioned not only had the most impressive writing but also the most affecting story lines partly because both of them were about love, although on the surface at least, of different kinds. Although they were self contained like most of the episodes they undoubtedly benefited from the viewers being acquainted with the back-story of Sargent Drake in the first case, and of Reed and Jane Cobden the social reformer in the second case (although it is not their relationship that is the centre of attention) and so I wouldn't recommend watching the episodes out of context. I just think it's worth bringing attention to these episodes in particular.
I have recently tried watching some of the other episodes for the second time and mainly because of the dialogue I have found this worthwhile even finding myself appreciating them more. This is one of those rare TV series which is worth watching more than once. Verse drama, or at least (free-)verse drama seems slowly to be making a comeback. We've already had Garrow's Law and now this. Interestingly Garrow tended towards the iambic and Ripper towards the trochaic.
For a very thought provoking discussion of the subject of literacy, language change and education over the last 150 years see 'Doing Our Own Thing: The Degradation of Language and Music, and Why We Should, Like, Care' (2003) by John McWhorter. He argues and provides evidence for the level of education (or practical aspiration) in the 19thc, and later, as enabling even the 'lower classes' to express themselves in an impressively articulate and even 'literary' way, especially in personal letters; and equally capable of understanding what they heard or read, on an intellectual level more like the Guardian Review than the Sun.