5 April 1946: birth of Jane Asher, who played Susan Foreman in Whatever Happened to Susan Foreman? (1994) and Andrea Yates in Whatever Happened to Sarah Jane? (2007), and has thus played alternative
5 April 1991: death of Gerald Blake, who directed The Abominable Snowmen (Second Doctor, 1967) and The Invasion of Time (Fourth Doctor, 1978).
5 April 1999: death of John Wiles, innovative producer who succeeded Verity Lambert but did not last long in 1965-66.
ii) broadcast anniversaries
5 April 1969: broadcast of fifth episode of The Space Pirates. The Doctor and friends find they have been imprisoned with the terrified Dom Issigri; Clancey and Dom escape, but the Doctor, looking for Jamie and Zoe, is caught in the take-off blast.
5 April 1975: broadcast of fifth episode of Genesis of the Daleks. The Doctor almost gets Davros to destroy the Daleks; Gharman leads a revolt against Davros; the Doctor prepares to blow up the incubation tanks.
5 April 2002: webcast of "No Child of Earth", part 2, the sixth episode of Death Comes to Time. (Am not going to bother with screenshots from this in future, they don't really tell us anything.)
5 April 2008: broadcast of Partners in Crime, first episode of Season Four of New Who; first regular appearance of Catherine Tate as Donna Noble. The Doctor and Donna foil a plan to turn large numbers of people into food for the infant Adipose.
5 April 2010: broadcast of Aeolian, thirteenth episode of the Australian K9 series. London is being bombarded by sound-waves that cause mass panic. K9 and Starkey are on the trail of an alien, the last of the Aeolians. Darius tries to rescue Jorjie, trapped by falling debris. Drake believes Gryffen has caused the catastrophe and sets out to destroy the creature.