Both The Faceless Ones and The Mutants reached their fourth episodes today - the Troughton story in 1967 and the Pertwee one in 1972.
Any doubts that the revived series was not a continuation of the series which had run from 1963 to 1989 were dispelled today in 2006 when Sarah Jane Smith returned to Doctor Who, bringing K9 Mk. III with her. This was in School Reunion.
Guest star Anthony Head had often been mentioned when it came to potential Doctor actors, and he had been considered for the role back in 1996.
The episode was designed to warn Rose that she could not stay with the Doctor forever, and considered what happened to the companions after they had been left behind. One issue with the story is that it rather glosses over The Five Doctors. Perhaps Rassilon wiped people's minds when they were all sent home after that story?