The BBFC is responsible for film classification in the UK, assigning ratings of U, PG, 12, 12A, 15, 18, and R18 based on factors like violence, sex, language, drugs and discrimination. The document discusses how the BBFC considers context, tone and impact, as well as imitable behavior, horror, violence, language, themes and sex when rating a film. It then explains that the film opening it refers to contains violence, themes of violence, smoking, imitable behavior, language and discrimination, so it rates the opening a 15.