27 April 1963 (incorrectly recorded here earlier this month as 17 April): birth of Russell T. Davies, head writer and executive producer of the first five years of New Who (2005-10) and author of Virgin New Adventure Damaged Goods (1996).
ii) broadcast anniversary
27 April 1968: broadcast of first episode of The Wheel in Space. The Tardis lands on a deserted spaceship; the controller of the nearby Wheel prepares to destroy it.
27 April 1974: broadcast of sixth episode of The Monster of Peldon. The Ice Warriors are defeated and the miners are reconciled with the Queen.
iii) date specified in canon
27 April 1986 or 1987: birth of Rose Tyler.