Series 5, Episode 6 – 'The Underground City'

Ace Iberian archaeologist Nikita might have nabbed a priceless magic carpet from a cavern, but now that the population of London is turning subterranean in pursuit of cheaper property prices, she may be the only one who can save humanity from the darkness. A thrilling tale, replete with excavated guacamole, lukewarm samosas, and precioussss things in the deep.