The red triangle was a warning system deployed by mainstream British TV station Channel 4 in the 1980s in order to warn viewers that the programme or film they were watching contained sexually explicit content or violence. It took the form of a small red warning triangle located in the top left of the screen.
The triangle system was a way of by-passing censorship laws and was an experiment undertaken with the ITC which oversees British television propriety and censorship. Usually it allowed the broadcast of foreign and/or art house films which until then had been banned.
It was short-lived, largely because it caused a national scandal that such content could be broadcast on British TV. It also had the effect of massively increasing audience figures amongst those who valued it as a form of legalised pornography.
