This episode – Revenge Of The Cybermen (1975)
The Fourth Doctor (Tom Baker), Sarah Jane and Harry return to Nerva (the Terra Nova Beacon?) in the 29th century to find a plague has killed off almost the entire crew. The Doctor immediately recognizes the same tired plan by the Cybermen and calls them out. But they’ve got another ace up their sleeve: destroying Voga, the Planet of Gold. Because that’s the only reason why they lost the Cyber Wars! It had nothing to do with human ingenuity, being outnumbered, or explosives. It was gold. Really.
Steve and Andrew try another interview, but accidentally hail the Vogons instead of the Vogans. Andrew is viciously attacked by a Cybermat, and both Steve and Andrew take shooting tips from the Vogans.