The Small Faces arrive at the docks with their manager Lester Benson (Kenneth Cope) to catch a boat out to Radio London, a pirate station operating from the middle of the sea. What Lester doesn't notice is that he has been photographed by a mysterious figure who may well be something to do with the diamond smuggling operation that the police are trying to foil, on both sides of the English Channel as the Dutch police have teamed up with the British law and have caught one of the most important players. Benson will soon find himself working for the smugglers as he is blackmailed about his shady past...
Written by Tudor Gates from an idea by executive producer Harold Shampan, Dateline Diamonds is a bit like watching two films vying for your attention at the same time. One is a solid British B movie, a type of thriller featuring a plot that wouldn't look out of place on television and would probably, in all honesty, be best suited to an episode of Z Cars or the like. The other is a vehicle to plug some bands and would-be singing stars, headed by an on the verge of being famous Small Faces who despite being the band Benson is managing and, you would expect, the centre of attention, barely get a scripted line between them.
Benson is being blackmailed by Major Fairclough (William Lucas), a dodgy military man who has found Benson's criminal record and means to exploit it for all it's worth. After turning up at his flat and interrupting his night of potential passion, the Major makes sure that Benson understands the mess he's in, and recruits him as a getaway driver for the diamond theft he's planned. And so it is that we are treated to the heist in full detail - it isn't Rififi but it'll do - as the Major breaks into the safe and makes good his escape, not counting on the presence of passerby Patsy Rowlands who gets a good look at him.
The police are represented by the long suffering detective Jenkins (Conrad Phillips) and his Dutch counterpart Verlekt (George Mikell), and a window into Jenkins' home life is provided as we see his teenage daughter (Anna Carteret) avidly tuning into the pirate radio. This is important because the diamonds are taken out of the country and onto the Radio London ship by Benson where they are taken by his contact there. This is also important because there is a small role for popular D.J. Kenny Everett, without the beard, where he awkwardly indulges in small talk with the actor playing the other D.J. and whistles at Jenkins' daughter's photograph which she has sent in for a request.
The acting is strictly functional, but the story is brief enough for it not to matter. However, you have to wonder at the audience's reaction at the time it was released: those keen to see the bands have to sit through the undemanding thriller plotline, and if there was anyone intent on following the story they'd be distracted by the musical numbers. As it is, the Small Faces only perform one song (although others are heard on the soundtrack), in a concert setting with close-ups so extreme they should have been renamed the Big Faces for this movie. The Chantelles get to mime to two tunes, and where are they now? The whole shebang ends with a minor car chase, and the law is triumphant, but you'll be left reflecting that excitement was thin on the ground. Nowadays novelty value is the best thing Dateline Diamonds has going for it.