I don’t think The Doctor is the only one who can open the door, nor is a key required in all cases. River Song showed him he can open it simply by snapping his fingers, and when he’s dubious, she proceeds to show him by doing it herself.
Yeah, it’s confusing because there’s a whole lot of canon running around about it. My preferred fan wank is that if the doors are just closed, the Doctor and companions can enter simply by pushing in as they often do in relaxed settings, but should a Dalek come aknocking, they have no access unless the door has been left open. There is a deadbolt, however, and when that deadbolt is locked, only a key will open the door.
waits for links to 8 different episodes that show my fanwank doesn’t hold water.
I didn’t really care for this episode. I found it rather boring. The wife liked it, though.
It seems like the first three episodes of every companion in New Who follows the same basic pattern.
In the first episode, aliens attack Earth, then in the second and third episode the Doctor takes them to a strange future alien world and some point in Earth’s past. Usually in the second episode the companion doubts the Doctor’s methods but realizes in the end that he’s right.