So he gets himself a new one?
The Doctor might be new, but the foe is not. To usher in Patrick Troughton as the Second Doctor, David Whitaker’s “The Power of the Daleks” (Story Production Code EE) relies on the everyone’s favorite aliens to ease the fledgling Time Lord (and the audience) into the new era. Viewers uncertain about William Hartnell’s replacement could still be expected to tune in for the Daleks, last seen some ten months prior. But, as is standard with Dalek stories, we do not see one until the end of the very first episode, leaving room for Ben and Polly to ask questions of this interloper, whose entire appearance and demeanor have changed.
Care is taken to reassure the viewer that there is a strong continuity between manifestations, particularly with a shot of Hartnell’s visage when Troughton looks into a mirror. The Doctor rummages through a chest and pulls out objects from past adventures, such as a dagger from Saladin and, ominously, a chunk of metal that causes him to mutter, “Extermination!” Oddly, though, he does not refer to himself as the Doctor once in the entire story, even referring to the Doctor in the third person during the first episode when asking if the Doctor kept a diary.

Viewership figures (as reported in Wood and Miles, About Time 2), come in at nearly eight million per episode for the six-part story, far stronger than those for recent stories like “The Smugglers” (less than five million per) and even “The Tenth Planet” (starting at five and a half million and peaking at seven and a half million as Hartnell exits). The audience, clearly, accepted Patrick Troughton, but do Ben and Polly accept the Second Doctor as the Doctor?
Polly does, almost immediately; her concern is whether this Doctor is so different that he will not want them along. Ben takes somewhat longer to warm to the idea. Clearly, this new figure knows his way around the TARDIS, flicking open the door switch without looking, but Ben calls him out for not checking the monitors to ascertain if it’s safe to leave. The Doctor drilled that notion into all his companions’ heads; if this strange figure doesn’t even bother, how could he be the Doctor? But the reply puts Ben rather in his place:
Oxygen density 172. Radiation nil. Temperature 86. Strong suggestion of mercury deposits. Satisfied, Ben? Now are you two coming or are you not?
The regeneration (a phrase not used in this story) is explained, broadly, as a function of the TARDIS. The exact phrasing—”I’ve been renewed. It’s part of the TARDIS. Without it, I couldn’t survive.”—leaves open the possibility that the Doctor’s life force is connected to the TARDIS not just for regeneration but for his very existence itself, bringing a hint of mystery to the ship that we haven’t seen since “Inside the Spaceship” back in the first season.

If “The Power of the Daleks” is known for anything, though, it should not be for the difficult task of selling the first regeneration as much as for making the Daleks scary again. An empire of Daleks can be (and has been) played for laughs; one Dalek is frankly terrifying.
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