Derek Gold- original name Derek Pratt- was a crooked gold dealer, so obsessed with gold that he even went to fancy-dress parties as Auric Goldfinger; his company ran ads claiming to offer clients big returns on their old jewelry while paying them a mere pittance. He also worked as a middle-man for various mob bosses, meaning that the gang would have to ensure that he thought the deal went wrong rather than suspect that he was conned or they would be left to deal with the mob.
He came to the gang's attention when Albert saw Vivian- an eldery woman who had fallen victim to his scam- crying outside of a restaurant where he was dining. Exploiting Gold's interest in war movies, the gang posed as a former Black Ops unit that had stolen a shipment of gold bullion while driving Gadafi out of the country, successfully putting Gold in contact with a fake German buyer (Really another of Albert's contacts). After acquiring various fake bars along with a genuine one, the group staged a meeting between Gold and Ash while Ash was dressed as a soldier on the run, Gold offering to help Ash with the sale of the gold.
Having provided Gold with the real bar to test its authenticity- the fake bars would only pass for the real thing from a distance to the experienced eye-, the group made the deal in a farmhouse with an army base nearby, allowing them to make it appear as though the army had caught them just after Gold had sent them the money. The 'German buyer' subsequently took the truck with the bars and drove away while leaving Gold with a fake check that he couldn't cash.
Although Gold found the gang in Eddie's bar based on a comment he had heard them making before the deal- they had assumed that he was too far away to hear them-, he assumed that the German had cheated all of them, accepting that the team hadn't been responsible, and offering them an additional £50 000 if they could provide proof that the German was dead given their Black Ops past, the team subsequently faking a photo of the man's corpse.