26 March 1925: birth of Barry Letts, producer of Who from Doctor Who and the Silurians (1970) to Robot (1974-75), director of Enemy of the World (1967-68) and The Android Invasion (1975), writer of The Dæmons (1972).
26 March 1966: broadcast of "The Bomb", fourth episode of the story we now call The Ark. The Monoids fight among each other; the Doctor and friends find the bomb on the Ark; and the Doctor turns invisible...
26 March 1978: broadcast of fifth episode of The Talons of Weng-Chiang. Leela and the Doctor go to the laundry and are followed by Jago and Litefoot who are captured. Leela and the Doctor return to Litefoot's house, where she unmasks Weng-Chiang.
26 March 2005: broadcast of Rose, the first episode of New Who. Rose Tyler meets the mysterious Doctor, and together they prevent the Autons / Nestene consciousness from taking over the Earth; and she decides to travel with him.