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Lydia Childs initially worked at Torchwood 1 as a secretary, having been born and raised in the area.
However, in 1918, on request of Gerald Kneale, Lydia re-located to Torchwood Three to take on a similar role. She was said to have possessed a remarkable memory and eclectic knowledge making her an invaluable member of the team. It was said that she often did not receive the thanks she deserved, a trait that seemed to plague Torchwood secretaries (such as Ianto Jones). She died before August in 1941. (PROSE: The Twilight Streets)
Behind the scenes
The full version of the photograph seen in the episode was released by the production team in The Torchwood Archives.