We first meet the Collector in this episode in a scene of pure, comedy gold, as a sycophantic Gatherer Hade informs him of the threat of unrest amongst the Ajacks. The best bits are the various cloying titles that the Gatherer bestows upon his superior - "Your Colossus, Your Pinnacle, Your Elevation". I could quote pretty much every line that made me laugh out loud during this episode, and indeed this story, but I would run out of time and room.
Similarly, the first (and only, as it would turn out) meeting between The Doctor and the Gatherer is equally enjoyable. Neither man is speaking truthfully, and both are concealing more than they are letting on. Tom Baker would ramp up the humourous side of his portrayal of The Doctor during the 1970s, but in this scene, he pitches it at just the right level.
Something must also be said about the sterling location work in this story in one of the rare cases of the production team using interior locations as something other than what it's supposed to be (for instance, the power plant location in The Hand of Fear looked fantastic...as a power plant). The endlessly long corridors that the team found match the equally long hallways needed in the script, as well as the interminable tax corridors that Robert Holmes was spewing hate for in this story in the form of clever, biting wit.