There are many really good British noir films that exploit the seediness of post-war London, set around Soho and involving realistic underground criminality and making very watchable drama out of 1950's London low-life.
But this isn't that kind of film.
For some reason, the producers decided to make a Hollywood type noir - ignoring the excellent genre work done by other British producers and creating a totally unbelievable poor-mans version of a movie that should have had Bogart and Raft in it but instead had a collection of totally out-of-place British actors - and - Jayne Mansfield.
Mansfield whispers - Marilyn Monroe style - her way through the part and it is obvious that her attempt at a sultry voice has to be overdubbed for many of her scenes. The rest of the cast try their best to be American gangsters (at one point Anthony Quayle actually calls somebody a "dirty-rat") and betray their true acting ability in a poor attempt to be something they aren't.
The cinematography is good - lots of moody lighting, clever angles and the direction is sharp, closely cut with some good set scenes. But you always feel that this is a British attempt at making a film that is totally un-British.
The film gets better as it progresses as the story takes over and Quayle's excellent performance lifts the film out of its misery into something that is finally worth watching. But you always feel that Quayle is on a damage reduction exercise trying his best to rescue the awful script and Mansfield's execrable acting and try and create something worthwhile. Regrettably, the forces of mediocrity win out.