Recurring actors in long running TV shows

It sometimes happens in a long running tv show that an actor will appear over the years in a few supporting roles, each time as someone different. This happened a fair amount in the Star Trek franchise, although they had it easy as someone could appear as a human one week, as a type 1 alien another week and as a type 2 alien the following week.

There are two long running British series that I watch every week: Casualty (now in series 26, Israel running about three months behind Britain) and Silent Witness (now in series 12, running about four years behind Britain). There have apparently been several actors who have played multiple characters in Casualty although I haven't been aware of this. As we only see one episode a week, it's easy to forget the extras.

But Silent Witness is shown every night (Sun-Thu), so we get through the episodes at a cracking pace. I've noticed two supporting actors who have appeared twice: Ruth Gemmell played a detective constable in all six episodes of the first series, but was 'killed' at the end of that series. Despite this, she made a remarkable recovery and appeared as a Detective Inspector in series nine or ten (not listed on IMDb). I know that dying (especially early) is a good way to sell records but apparently it also helps one's police career.

A rather more egregious example is that of Ciaran McMenamin, who played the part of Prof Sam Ryan's hitherto unknown son in episodes 1 and 2 of series 8, the final episodes of Ryan (Amanda Burton). In these episodes, he played a surly and unpleasant Irishman. Lo and behold, in episodes 5 and 6 of series 12, he once again plays a fairly major part, also as a surly and unpleasant Irishman.

In the first few series of SW, each series featured an unvarying police team (hence the multiple appearances of Ruth Gemmell as a dc) but since then, there have always been new policemen every week ... except once, when Paul Panting played the part (alliteration running wild for a minute) of DCI Mumford in a few different episodes. How this policeman rose to the exalted rank of Detective Chief Inspector is beyond me as he doesn't seem to be a very good policeman. The same actor apparently played the part of 'Gordon' in one of the earliest episodes but didn't trouble my memory then.