Second paragraph of third chapter:

Even while screaming, part of the Doctor’s mind analysed the problem. They were falling towards something, which most likely meant they were dropping towards a planetary surface. Based on the rate of their descent, he made a guess at the strength of the planet’s mavity. Then he ran that information through a complicated calculation involving the number of seconds they had been in freefall and came up with an estimate that they had so far fallen 30,000 feet.

The Well was my favourite of this year’s Doctor Who stories. I wrote of it:

Midnight is (still) my favourite Russell T. Davis episode, and I must admit I was delighted when The Well turned out to be a sequel, with a real base-under-siege plot and a really scary monster. We had more mind-blowing stuff to come this season, but this was the scariest episode by far.

I was a bit surprised by the news that Gareth Powell had been assigned the job of writing the novelisation – I don’t think he has published any other tie-in literature, instead developing his own complex universes. But it makes perfect sense – Powell’s writing is definitely on the more advanced side of military SF, and The Well is the most military Doctor Who story for years; the Doctor and Belinda even change into military uniform, before the horror part of the story gets going.

And of course it’s a good piece of work. A lot of the appeal of the episode was visual, which can be difficult to translate onto the printed page, but Powell actually uses this for freedom to explore the rather small world of the Well and its visitors a bit more. The story is broken up by brief bios of the military characters, fleshing them out a bit more than we got on screen. The tension of the plot is effectively maintained. I felt pretty satisfied. You can get Doctor Who: The Well here.