i) births and deaths

2 February 1930: birth of Don Houghton, who wrote Inferno (Third Doctor, 1970) and The Mind of Evil (Third Doctor, 1971)

2 February 2011: death of Margaret John, who played Megan Jones, the Director of Euro Sea Gas, in Fury from the Deep (Second Doctor, 1968) and The Idiot's Lantern (Tenth Doctor, 2006), a 38-year gap which is unmatched for the main TV show (spinoffs allow some flexibility)

ii) broadcast anniversaries

2 February 1974: broadcast of fourth episode of Invasion of the Dinosaurs. Sarah is indoctrinated by the People; the Doctor is framed as the man behind the appearance of the dinosaurs.

2 February 1982: broadcast of second episode of Kinda. The unhinged Hindle takes over the base; Todd returns, equally out of his mind; Tegan, possessed by the Mara, takes over Aris.

2 February 1983: broadcast of second episode of Mawdryn Undead. The Doctor meets the Brigadier and shocks him into remembering his previous incarnations; Tegan and Nyssa meet the younger Brigadier, and then a man with no top to his skull.

2 February 1984: broadcast of third episode of Frontios. Turlough remembers his own world's lore about the Tractators, who still have Tegan and the Doctor trapped in the tunnels.

2 February 1985: broadcast of first episode of Mark of the Rani, introducing Kate O'Mara as the Rani. In 1820s England, the Rani's experiments, aided by the Master, are turning locals into violent Luddites.

2 February 2020: broadcast of Praxeus. What connects strange bird behaviour in the skies above a Madagascan beach to mysterious deaths by a deadly virus that seems to be spreading? And what does a famous British astronaut have to do with all of this? Can the Doctor, Ryan, Graham and Yaz solve this puzzle before it's too late?