21 April 1927: birth of Gerald Flood, who played Kamelion in 1983 and 1984, and also King John in The King's Demons (1983).
21 April 1935: birth of Anthony Read, script editor of Doctor Who from Underworld (1978) to The Armageddon Factor (1979), co-writer of The Invasion of Time (1978) and writer of The Horns of Nimon (1979-80).
21 April 2002: death of Terry Walsh, stuntman and actor in many Old Who stories.
ii) broadcast anniversaries
21 April 1973: broadcast of third episode of Planet of the Daleks. The Doctor and the Thals escape from the Dalek base.
21 April 2007: broadcast of Daleks in Manhattan. The Doctor and Martha land in New York in 1930 where the Daleks are attempting to merge with humans.