The BBFC has now updated its page for Prometheus to give Extended Classification Information, i.e. a more detailed reason why Prometheus was rated 15 in the UK. It does contain spoilers about what happens to certain people in the film. I don’t think this list is conclusive, it just gives examples of some of the gore that contributed to the rating.
The film contains a number of scenes of strong violence that feature heavy blows and bloody detail. For example, in one scene a character’s arm is broken, revealing blood and bone, and in another scene a character’s head is smashed against the floor, resulting in a large spurt of blood. This emphasis on bloody detail exceeds the terms of the BBFC’s Guidelines at ’12A’/’12’ and is more appropriately classified at ’15’ where the Guidelines state ‘Violence may be strong but should not dwell on the infliction of pain or injury’. There are also some scenes featuring gory detail, both when dead bodies are seen and when people are injured. One scene features some gory surgical detail that exceeds the type of ‘occasional gory moments’ that may be permitted at ’12A’.
The Guidelines at ’12A’/’12’ also state ‘Moderate physical and psychological threat may be permitted, provided disturbing sequences are not frequent or sustained’. The second half of the film in particular features a sense of threat towards the central characters that is both frequent and sustained.
PROMETHEUS also includes one use of strong language and one implied use of strong language, when a remark is broken up by static. It also includes some undetailed verbal sex references and a brief scene in which a couple start to have sex, without any nudity or other detail.
Thanks to Cvalda for the news.