Red triangle (Channel 4)

The red triangle was a content warning system employed by mainstream terrestrial British television broadcaster Channel 4 for a brief period from 1986 to 1987. A similar warning had been briefly used by ATV in the 1970s (a white rectangle) - to warn viewers of potentially disturbing material.^[1]

The channel showed a number of mainly 18 certificate art films in the early hours of the morning as part of the "red triangle" series, gaining unexpectedly large audiences. After lobbying from newspapers and pressure groups this method of identifying such material was discontinued.