As content became more explicit, the industry developed formal systems to warn audiences while allowing mature themes to flourish.
In the mid-20th century, mature content in English media was defined by the struggle against censorship.
: Between the late 1950s and mid-1970s, British cinema saw an explosion of "X-certificated" films. This era, often called the "long 1960s," pushed limits on violence, horror, and sexuality as filmmakers fought for artistic freedom against the British Board of Film Censors (BBFC) .