In this and almost all episodes, Catweazle recites "Sator, Arepo, Tenet, Opera, Rotas" as a charm. This is the oldest magic square known to man, found in the ruins of Pompeii. It is palindromic and, when you write the five words one atop the other, the same words can be read in order left to right, top to bottom or right to left bottom to top.