- Deleted Scene: Hal originally had an introductory scene that featured the archer flirting with a serving girl named Mary, and explained that he had accompanied Sir Edward on one of the Crusades, helping him return home after falling sick in the Holy Land. The loss of this sequence resulted in the omission of all of Mary's dialogue from the finished serial and, as a result, actress Jacqueline Stanbury would no longer be listed in the credits.
- First Appearance: Of Sarah Jane Smith and the Sontarans. It also marks the first time that the Doctor's home planet, Gallifrey, is referred to by name.
- Money, Dear Boy: Robert Holmes claimed he took on the assignment, despite disliking historical stories, because he needed the money.
- The Other Marty: April Walker was originally cast as Sarah Jane Smith. However, when Jon Pertwee showed his dissatisfaction of her casting (according to him, her stature was too strong to fit the role of a Doctor Who companion), then-producer Barry Letts recast Elisabeth Sladen in the role with Pertwee's approval.
- What Could Have Been:
- Barry Letts wanted Bob Hoskins to play Irongron. He was unavailable, but he did recommend David Daker.
- In the original script, it was the Doctor who killed Linx by shooting an arrow into his probic vent.
- According to the trivia subtitles on the DVD, the entire UNIT Dating Controversy could have been avoided apparently a cut line from the sequence where Linx interrogates Sarah Jane would have had her specify that she came from the year 1974.
- The original script contained a full scale battle scene of knights in armour attacking the castle. Terrance Dicks realised that this was way beyond the show's budget, so he changed it to the Doctor repelling invaders with smoke bombs.
- There were talks about reataining Hal as a second companion and Barry Letts approached Jeremy Bulloch to enquire about his schedule, but nothing came of it.
- Working Title: The Fugitive, The Time Fugitive and The Time Survivor.
- Writer Revolt: Robert Holmes hated the idea of writing a historical story, as he found them "whimsical and twee", in part because of how many of them involved the Doctor coincidentally meeting famous historical figures, so he came up with a story about an alien in the Middle Ages with no connection to anyone noteworthy whatsoever.
- You Look Familiar: Jeremy Bulloch (Hal) was also in "The Space Museum".
Trivia / Doctor Who S11 E1 "The Time Warrior"