Q.E.D. (quod erat demonstrandum, Latin for "that which was to be demonstrated") was the name of a series of BBC popular science documentary films which aired in the United Kingdom from 1982 to 1999. Running in a half-hour peak-time slot on the BBC's primary mass-audience channel BBC1, the series had a more populist and general interest agenda than the long-running Horizon series which aired on the more specialist channel BBC2. Horizon could often be difficult for a scientific novice, requiring a modicum of background knowledge beyond the reaches of many viewers, so Q.E.D. was a more approachable way of introducing scientific stories.