This is one of the most shocking films ever made about the true depths of colour prejudice in Britain in the 1950s, and the violent hatreds of black people harboured at that time by the white British working classes, especially in London. The film is well-scripted, and boldly directed by Basil Dearden, and it shows without flinching the true state of feeling as it was in those days (with some strong anti-white prejudice by blacks thrown in, to demonstrate that things are never only one way). What is so utterly horrifying about watching all of this now is, that it really was all true then. It is inevitable that some of the characters both white and black should resemble stereotypes, perhaps for the reason that at that time, people genuinely were stereotypes. The story concerns a police investigation of a murder of a young girl who was a student at the Royal Academy of Music (half way through the film a policeman calls it the Royal College of Music; Londoners are always confusing the two separate institutions in that way, so perhaps this script flaw merely reflects real life). Her body is found on Hampstead Heath in London, and there are no clues apart from the initial 'S' (her name is eventually discovered to be Sapphire). As a crime investigation thriller, the film is solid and extremely well done. A spectacular cameo performance is given by the black actor Robert Adams as 'Horace Big Cigar', not long before he died. The acting is all reliable and convincing. Dearden is especially good at not allowing any of the women and children to scream when discovering a body or having a horrible experience: his technique was extremely subtle, and they instead stifle screams, a scream begins to form, and then they put their own hands over their mouths in horror. When identifying a corpse, the actor behaves as one would naturally do, with numb paralysed shock, remaining silent and staring. All the ridiculous Hollywood histrionics and stock reactions of approved hysteria and screaming females are eliminated from this very British film, in which there is no place for hysteria except with one black character who panics for story reasons. Sociologists should really see this film. However, it is so incendiary that I cannot see it ever being released again or even being shown on television, at least not in Britain. In fact, some of the comments in the film may even have become 'illegal' under the harsh new race relations laws, even in a fictional context! Anyone who thinks race problems have gone away does not know human nature. Sensitivity to small differences, such as skin colour, is so firmly rooted in animal behaviour (the isolation by the herd of the black sheep, the driving away of albino animals from the pack), that race hatreds are inescapable, and can only be suppressed, never eradicated. Seeing this film reminds one of this depressing aspect of life by a blatant portrayal of it which is almost too painful to watch.