27 April 1928: birth of Hubert Rees who played the Chief Engineer in Fury from the Deep (Second Doctor, 1968), Captain Ransom in The War Games (Second Doctor, 1969), and Stevenson in The Seeds of Doom (Fourth Doctor, 1976).
27 April 1931: birth of Glyn Jones, one of the few people who not only wrote a TV Who story - the story we now call The Space Museum (First Doctor, 1965) - but also appeared on the show as an actor, playing stranded astronaut Krans in The Sontaran Experiment (Fourth Doctor, 1975). See his autobiography.
27 April 1963: 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). Without him, there would be no New Who.
27 April 1974: birth of Joseph Millson, who played Maria's father Alan Jackson in the first two series of the Sarah Jane Adventures.
27 April 1982: birth of Samuel Anderson, who played Clara's boyfriend Daniel Pink in the eighth series of New Who (2014)
Speaking of whom, 27 April 1986: birth of Jenna Coleman, who played Clara herself in the seventh, eighth and ninth series of New Who, as well as appearances before and after between 2012 and 2017.
ii) broadcast anniversaries
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 Peladon. The Ice Warriors are defeated and the miners are reconciled with the Queen.
27 April 2013: broadcast of Journey to the Centre of the TARDIS. The Doctor's TARDIS is captured by space salvager brothers and Clara gets lost inside it. The Doctor promises the brothers they can have the TARDIS if they'll help search for her. They agree, only to find that what lies at the centre of the TARDIS can kill them all.