"Doctor Who" has always been at its best when veering more towards horror than science fiction and although both "The Impossible Planet", and its conclusion "The Satan Pit", are dressed in sf iconography this two-parter is ultimately a tale of terror. It may be set on a planet improbably orbiting a black hole, which could well be read as a metaphor for the irrationality of any religious belief system, in that trust in a supernatural being is fundamentally empty for not being grounded in the laws of physics, but this was a story dealing with the impulses that steer human beings away from the light and into the dark. The steel cable in the lift shaft snaps because the Beast in the pit doesn't want the Doctor's voice of logical scientific reasoning to be heard above its putting the fear of God into the personnel of Sanctuary Base 6.
And, in the Beast, what a voice to be tempted by! Gabriel Woolf makes a remarkable return to "Doctor Who", after an absence of 31 years, having last appeared as Sutekh the Destroyer in the fourth Doctor story "Pyramids of Mars". It is particularly striking in the closing stages of "The Satan Pit" when acting-Captain Zack, Danny boy and Rosebud are fleeing certain death, confined together in a spaceship, as a fire-breathing Toby reveals himself to be still possessed. I suspect that children would've found this more frightening than the superbly realised computer-generated monster itself. On this level, this story is pure Boys' Own stuff. The rocket taking off is straight out of one of those annuals you get for Christmas and, as a result, makes episodes eight and nine oodles more like old "Doctor Who" than anything that has gone before!!