Much of the "hand wringing" and other actor mannerisms discussed on this thread drive acting coaches and directors nuts! However, in the high stress world of semi-live tv, many of these quirks were useful for the actors in focusing themselves and dealing with their nerves(take note of how sometimes the hand-wringing, etc. becomes intensified when an actor has obviously "dries up," or forgotten their lines!).
And, as I'm sure you'll agree, many of these quirks became identifiable with the character, rather than the actor who played the role. An example of a more thought out mannerism would be Prof. Stokes use of his monocle, or the way that, say, Nicholas Blair moves through space as opposed to Willie (status can be illustrated through physicality).
In many ways, the actors who were under day-to-day stress of a more-or-less live show were employing whatever survival techniques they had at their disposal. By the way, knowing what to properly do(or not to do) with one's hands while onstage is among the trickiest skills to learn, along with practicing stillness, and just listening to the other actors! Many, though not all, of the actors who were "guilty" of nervous mannerisms on the show were actually quite inexperienced, particularly in the tv medium.
In spite of what many people think of Anthony George's performance on DS ("Burke Lite," etc.), you will note that his physical presence is consistently smooth and unhampered by these nervous ticks. Perhaps his previous experience in television aided him- or perhaps he had an acting coach that stressed physical discipline. Conversely, for all his physical discipline,he never really developed any distinctive, purposeful mannerisms that made viewing or listening to him more interesting.
Petofi
