The Doctor Who Production Diary: May 21st

1965 Maureen O'Brien's contract is extended through the fourth episode of the third production block Vicki
1965 Peter Purves is contracted to play the new companion, now called Steven Taylor, through the fourth episode of the third production block Steven 
Taylor
1965 Recording for The Chase takes place in Riverside Studio 6 The Chase
1966 The debut broadcast of The Gunfighters episode four, The O.K. Corral, on BBC1 achieves Doctor Who's lowest-ever Audience Appreciation index: 30% The Gunfighters
1969 Jon Pertwee is contracted to play the Third Doctor for at least twenty-one episodes The Third Doctor
1970 Recording for Inferno takes place in BBC Television Centre Studio 3 Inferno
1974 A labour dispute cancels recording for Robot in BBC Television Centre Studio 3 Robot
1979 Recording for City Of Death takes place in BBC Television Centre Studio 3 City Of Death
1980 Filming for State Of Decay takes place at the BBC Visual Effects Workshop State Of Decay
1981 Recording for The Visitation takes place in BBC Television Centre Studio 3 The Visitation
1987 Location filming for Paradise Towers takes place in Chalfont St Giles, Buckinghamshire Paradise Towers
1996 The FOX network announces its Fall 1996 schedule; Doctor Who is not included, with poor ratings prompting the network to drop the programme The Eighth Doctor
2005 Debut broadcast of The Empty Child on BBC1 The Empty Child / The Doctor Dances
2009 Recording for The End Of Time takes place at HTV Wales Studios in Cardiff, Wales The End Of Time
2011 Debut broadcast of The Rebel Flesh on BBC1 and BBC1 HD The Rebel Flesh / The Almost People