The story of Diamond City takes place in the South African diamond fields during the latter half of the 19th Century and indeed much of the filming took place on the actual land where the events actually took place. Stafford Parker (David Farrar) is a self appointed peace-keeper in Hopetown, nearest settlement to the diamond fields. It is 1870, and when news spreads of a big find Stafford Parker hurries off to see the old chief, in whose land the find was made. Stafford asks the old chief (Norris Smith) to grant him the concession to work the new diamond fields as the sole agent. Whilst they are talking, the old man’s nephew arrives with a counter proposal from his employer, the unscrupulous rum-dealer and illicit diamond buyer, Muller (Niall McGinnis). Stafford gets the concession but has to convince Muller to accept his authority in a fist fight. Muller appears to agree to Stafford registering the claims and administering the town, however he continues to plot and scheme. When Stafford finds a big diamond on his own claim he gives it to Mr. Pinto (Bill Owen) to cut as a gift for Dora Bracken (Diana Dors) who helps her mother run the local hotel. Stafford then meets Salvation Army lassie Mary Hart (Honor Blackman) who together with her father (Mervyn Johns) is planning to civilize the hard drinking and hard living community. Whilst Stafford is bemused by their naivety, his is impressed by Mary’s beauty. Meanwhile David Raymond (Andrew Crawford) a young, handsome digger and Stafford’s best friend is also taken by Miss Hart’s charm and beauty and very soon falls in love with her. Their romance is disturbed by a lynch mob hanging an illicit diamond buyer. Meanwhile Dora is leading the chorus in the town theatre, but her heart is heavy for she has realized that Stafford is smitten by her Salvationist rival. Dora loves him so much that she is prepared to relinquish him to the other woman if that will make him happy. Dora meets Stafford in his office to return his diamond when they are interrupted by a deputation of townsmen who want to form a Diggers’ Republic. Muller has now organized his own small army to take control of the town but is repelled vigorously by Stafford and the Diggers. Unfortunately young David is wounded but a few days later the infant Republic is formally handed over to the British who soon restore law and order. With David wounded, Mary realizes that it is he that she truly loves and advises Stafford accordingly. Therefore Parker packs his wagon determined to leave the past behind him and satisfy his desire for more adventure. As he is about to leave Dora runs to join him; he then realizes that they will never be parted.