1 May (production)


 * 1969 - David Whitaker was commissioned to write The Ambassadors of Death, then known as The Carriers of Death. Full scripts were requested nearly two months later.
 * 1974 - The final studio recording session for Planet of the Spiders and for Jon Pertwee was held. Tom Baker, already in the midst of production of his first story, attended and filmed a regeneration sequence.