The Parting of the Ways
Pauline Collins appeared previously in the series as Samantha Briggs in the Second Doctor serial "The Faceless Ones" (1967). This makes her the third actor from the classic series to appear in the new series, following William Thomas ("Remembrance of the Daleks" and "Boom Town") and Nisha Nayar ("Paradise Towers" and "Bad Wolf"/"The Parting of the Ways"). Collins had been offered a role as a companion in 1967, but had turned this down. According to the accompanying episode commentary, actor Tom Smith, who played the Host, attended drama school with David Tennant.