Nicky Ladanowsky and Nicola Bryant also appeared as different characters in previous episodes.
Keith Barron and Nicola Bryant have both appeared in Doctor Who, especially alongside Peter Davison's 5th Doctor. Keith Barron played Captain Striker in Enlightenment (1983) and Nicola Bryant played companion to both 5th & 6th Doctors from Planet of Fire (1984) to The Trial of a Time Lord (1986) and again in Dimensions in Time (1993).