On 21 May, the following important behind-the-scenes events were known to have occurred:
- 1965 - "Journey into Terror" was recorded at Riverside Studios 1. (TCH 5)
- 1969 - Jon Pertwee signed his contract for his début season as the Third Doctor.
- 2008 - The BBC formally announced Russell T Davies would step down as executive producer of Doctor Who in 2009, to be succeeded by Steven Moffat.
- 2008 - Recording for The Doomwood Curse took place at The Moat Studios.
- 2019 - Recording for The First Doctor: Volume Three took place.
- 2019 - Recording for Heritage 2 took place at The Soundhouse.
Community content is available under CC-BY-SA unless otherwise noted.