1974 – the year that Tangerine Dream released the album Phaedra.
This is… The 6-episode serial which is the Third Doctor’s last.
Broadcasts: Saturdays, May and June 1974, about 17:40 or so (varies) on BBC One.
World of Fandom: The 2009 DWM readers’ poll of 200 stories – ranking #89.
Product: On Doctor Who DVD. Plus streaming on BBC YouTube.