April Books 15) The Romance of Crime, by Gareth Roberts
I liked this much more than the other Four / Romana II / K9 novel I've read, The Well-Mannered War, which as it happens is by the same author. Our heroes arrive on a sinister prison asteroid, where they find themselves at the centre of a plot involving miners, corrupt judges, criminal brothers based on the Krays, Ogrons, and a dead mind-stealing criminal. The Doctor accuses K9 of never knowing the answer when it's something important, a glorious reference to the famous Tom Baker out-take. It all pretty much hangs together, Russell juggling multiple viewpoint characters without losing track of the story. One of the good ones.