Mightygodking.com -- Susan’s Shadow
Chris Bird nails it in one.
Because the first pretty young woman the Doctor traveled with, back when he was an old man played by William Hartnell, was his grand-daughter Susan. (Also more contentious than sex: Whether William Hartnell was the actual first incarnation of the Doctor, or just the first we’ve seen.) The two were inseparable, each one the only reminder the other had of their home, and the original stories tended to focus on the differences between them and the humans that shared the TARDIS with the Doctor. (When Carole Ann Ford, the actress who played Susan, left the series, some speculated it wouldn’t survive her departure.) Susan’s departure was a watershed moment, a coming of age as the Doctor finally realized that staying with him was preventing her from living her own life. He forced her to stay behind with the man she’d come to love in one of the most bittersweet moments of the show’s history.
And the subsequent episode makes explicit what all the subsequent stories would leave as subtext. Ian and Barbara, the Doctor’s human friends, convince him to adopt a young orphan woman they’ve rescued from a crashed starship as their new traveling companion. Vicki becomes a surrogate grand-daughter to the Doctor, someone who makes him feel young and alive as they share the wonders of exploring the universe together…until she also falls in love with a boy and leaves. And the Doctor found another surrogate for Susan, and another, and another…at heart, Doctor Who is a series about a lonely old man who’s lost his family, and who finds it again with an orphaned girl. (This is the one really big mistake the new series makes with Rose, I think; not that she loves the Doctor, but that she only travels with the Doctor by choice. All the best companions of the old series were running away from something.)
Not every companion is living in Susan’s shadow, of course; Romana, for instance, seems to be pretty blatantly shagging the Doctor off-screen. (Mainly because Lalla Ward and Tom Baker pretty much were blatantly shagging each other off-screen. But now is not the time to delve into the vast store of gossip about who was having sex with who on the set.) But that’s the model of Doctor Who. That’s the reason why all the jokes about “What is the Doctor doing with those pretty young girls between adventures?” miss the point. The Doctor has a father’s love for his companions, not a romantic passion. There is most definitely a difference.