Aside from Felix Aylmer's appearance as the President of his South American country, I hadn't really heard of many of the cast of jobbing British actors drafted in for this amiable crime caper. High-roller "Mortimer" (Donald Stewart) is determined to close a big deal but is neglecting his increasingly bored wife "Teri" (Anne Crawford). Intent on getting his attention, she goes to an high-end jewellers where she has discovered the eponymous diamond is being sold. Now one of her husband's underlings has alerted his boss to her visit and once they are both there, things start to hot up! A robbery is afoot, and with the help of some rather potent perfume she is relieved of her new jewel and the police are soon on the case. Later that evening they attend a state dinner with the aforementioned president and it's there that they realise that their charming and debonaire robber is also in attendance - in the guise of an influential businessman. Can they retrieve the stone - and the state jewels that have also been pilfered - before this character makes good their escape? At times this borders on the farce, but it is pretty well executed with good timing and just a little more sophistication to keep the pot boiling. Certainly, it's twenty minutes too long and the ending stretches out the theme a bit too far, but for the most part it's an enjoyable outing for Crawford and for Charles Helsop as long-suffering aide "Dilfallow" that moves along with a bit of style and a decent pace.