The penultimate appearance of Alastair Lethbridge-Stewart on Doctor Who (1963), save for an appearance in the one-off charity episode Doctor Who: Dimensions in Time (1993) (though the canon status of that special is in doubt). Although the character has been mentioned in episodes of Doctor Who, he did not appear in the revived series. Nicholas Courtney would reprise the role in 2008, however, as a guest star in a two-part episode of The Sarah Jane Adventures (2007).
The final episode of the classic era to see the TARDIS interior (especially in it's 1980's design). The TARDIS interior was never shown for the rest of Season 26 until Doctor Who: The Movie (1996) seven years later.
When Sargeant Zbrigniev tells Brigadier Bambera about The Doctor and that The Doctor was the scientific advisor of UNIT, which Brigadier Lethbridge-Stewart was Zbrigniev's commanding office, Zbrigniev mentions that The Doctor changed his appearance several times. The Brigadier first met The Doctor when he was in his 2nd incarnation (Patrick Troughton). The Brigadeer did meet The 1st Doctor (William Hartnell), whom appeared on the TARDIS scanner and again in the Black Tower in the Death Zone on Gallifrey. But The Brigadier did not meet the 6th Doctor, but later briefly encountered him in the 30th anniversary special Dimensions in Time and later met him in the audio adventure "The Spectre of Lanyon Moor".
23 years earlier. Nicholas Courtney and Jean Marsh appeared together in the epic 1966 story "The Dalek Masterplan" starring William Hartnell as the 1st Doctor. Nicholas Courtney played Bret Vyon and Jean Marsh played Sara Kingdom.
Attracting only 3.1 million viewers, this episode has the dubious distinction of being the lowest rated episode produced during the original 26 year run of Doctor Who (1963).