Landmarks No.34

The Curse of Fenric.
At the same time that we are being drip-fed the new, darker, Doctor, something else has been going on. There's a story arc - and it isn't necessarily about the Time Lord.
There's more to that arsonist, anti-social brat he picked up on Iceworld than we realised.
At the time, we just accepted that she traveled from present day Perivale to Iceworld thanks to a time-storm which appeared in her bedroom one day. A side effect of mixing up home-made explosives apparently.
Just bad science, most of us thought at the time.
Later, in Silver Nemesis, the Doctor is intrigued about a chess game in progress in Lady Peinforte's study.
Again, most of us didn't think much of this at the time. We also learned of a cut scene in which Ace saw a portrait of herself in Regency dress at Windsor Castle.
We know Ace is a troubled girl - with a deep resentment for her mother - and she has a friend who has been the victim of a hate crime.
Ghostlight fleshes out this back-story a bit more. We find that Ace burned down Gabriel Chase in the 1980's.
With The Curse of Fenric, things are pieced together. Fenric, an ancient evil once beaten by the Doctor through a game of chess, has been manipulating a number of individuals and families through time in order to free itself and exact revenge upon the Doctor. Ace turns out to be one of these pawns.
By sending Kathleen Dudman to stay with her grandmother in South London, Ace creates her own existence. Kathleen's baby, who Ace dotes on, is going to grow up to be the mother she hates.
For the first time, the companion has become the main focus of attention. They're not there just to scream, get into trouble, create jeopardy and make the Doctor look clever and brave.
The new series, from 2005 onward, has followed the same course - leading some fans to actually complain that the Doctor has become second billing in his own series.
I wouldn't go quite that far myself, and we have to accept that the 1960's & '70's representation of the companion just isn't acceptable anymore.