Out of the Unknown (partially found BBC sci-fi series; 1967-1971)
Out of the Unknown was a British sci-fi anthology series that aired from 1967-1971 that was produced by BBC and aired on BBC2 in four series. The stories were dramatisations of sci-fi short stories, and while most were of already published stories, some were written for the show
Loss of the Episodes
Like many other BBC shows of the time, during the early 1970s, a number of episodes were wiped so the tapes could be re-used. A total of 49 episodes were produced and aired on BBC2, however, only 20 of these episodes still exist in their entirety, mostly from series 1. There are a few episodes that have small video clips existing, complete audio recordings of episodes, and small audio clips without video of some lost episodes. Off-screen photographs, known as tele-snaps, were taken of many first and second series stories including some of the missing episodes. 
All of the surviving episodes were released on DVD in November of 2014 by the BFI.