6 July 1979: death of Malcolm Hulke, co-author of The Faceless Ones, The War Games and (uncredited) The Ambassadors of Death, sole author of Doctor Who and the Silurians, Colony in Space, The Sea Devils, Frontier in Space, and Invasion of the Dinosaurs, and writer of seven novelisations (DW&t Cave-Monsters, DW&t Doomsday Weapon, DW&t Sea Devils, DW&t Green Death, DW&t Dinosaur Invasion, DW&t Space War and DW&t War Games) and co-writer of The Making of Doctor Who. His stories showed a commitment to politics and a mild obsession with reptiles.
ii) broadcast anniversary
6 July 2009: broadcast of the first episode of Torchwood: Children of Earth, with the children stopping in place and chanting, and sinister goings-on at the top of the government; at the end Jack gets blown up in the Hub, and the wains chant "We are coming back". Thrilling stuff.
Edited to add: iii) dates in televised stories
As alex_wilcock points out, 6 July was also the planned date of The Android Invasion.