I started watching Doctor Who one year and nearly two months ago. Last night, I finished the original series run when I watched the final episode of the seventh Doctor serial Survival. At twenty six seasons, it's a remarkably cohesive story. Soap operas are known to run for decades, but those few characters who persist throughout the series are unrecognisable in their older episodes, plots frequently contradict as a writer's familiarity with older episodes isn't typically deemed important and there are even famous examples of characters who disappeared because the writers simply forgot about them. Despite some changes to his character both intentional (personality changes with regeneration) and possibly unintentional (whether or not he can do magic tricks, is a capable martial artist), the Doctor remains a clear thread throughout the series and despite some serials being similar, the show managed to never really repeat itself. It managed to continue with its own distinct identity while successfully incorporating new ideas--the more comedic second Doctor, the action oriented third, the more personable fourth.
Apparently the seventh Doctor's final three serials are referred to as the "Ace trilogy" because they all in some way deal with the personal life of the Doctor's companion Ace. Ghost Light was one of my favourite serials of the whole series, taking place entirely in a large house in the Victorian era, over a hundred years before Ace, as a child, encountered the, to her, haunted place which permanently marked her psyche. The serial successfully ties together themes of evolution, need, and fear of confrontation all while being atmospheric.
Curse of Fenric was somewhat less successful--the third seventh Doctor serial to feature references to Norse mythology, which I liked, it did have a great World War II meets supernatural pulp plot, nice location shots, and genuinely creepy underwater vampires. The foreboding in the Doctor's casual warning to Ace not to go into the water was nice, and it was a funny counterpoint when Ace refused to join her new friends in the water by saying, "Swimming is stupid!"
Her new friends were well cast, sturdy wartime broads.
The serial ended somewhat awkwardly with Ace's pathos card being played a little too far.
The final serial, Survival, featured the Master but was still a fairly smart story about the idea of life necessarily coming at the cost of other lives. In fact, the three serials seem to have an ongoing communism versus capitalism theme--or coexisting peacefully versus survival of the fittest. Ghost Light featuring a ruthless alien intelligence directing the evolution of some species for his own ends, Curse of Fenric waxes romantic about the Russian Revolution, and Survival discusses the idea of a better nature in humans overcoming the primal predator/prey dichotomy. The previous season had featured the anti-Margaret Thatcher story The Happiness Patrol, so it would seem to be a progression to a more overtly leftist ideology. That it's paired with explorations of Ace's character seems to me perhaps a statement about youth damaged by an adult society attached to hierarchies.
It's certainly interesting in light of the more positive perspective on the British establishment in the first and third Doctors' eras--though, again, it's nothing that would create real contradictions in the character of the Doctor in the different eras.