One of the high points of Series 2 was the episode School Reunion, which featured not only Sarah Jane Smith and K-9 but some excellent new monsters, the Krillitane, too. These bat-like reptilian foes didn't menace the Doctor alone, though. They had the help of their human-like leader, Mr Finch (played to marvellous effect by Anthony Head). Mr Finch is acting as the Headmaster of a school in Deffry Vale, but is secretly using the schoolchildren to try and crack the Skasis Paradigm. If he succeeds, the Krillitanes will attain the power to change the universe as they see fit - not a pleasant proposition for all the other species in Creation. Knowing that Finch is up to something, but not sure what, the Doctor confronts the Headmaster by the side of the school pool. The tense exchange ends with a line that defines the entire year of stories, if not much of the Tenth Doctor's era: "You get one warning. That was it." The line is delivered in a way that leaves no doubt the Doctor is deadly serious. Not that it detracts from the power of the scene, but it's pretty unusual for a school in England to have a pool!