Sarah Siddons

Sarah Siddons was an individual who was famous on Earth and known to people in England. She was deceased (AUDIO: A Photograph to Remember) by 1888 (WC: The Battle of Demons Run: Two Days Later) and after her death the Sontaran Stonn devised a plan with his partner Tom Foster to take photographs of people with cardboard cut-outs of famous dead people, including Siddons and Charles Dickens. Their plan was uncovered by Jenny Flint, Strax and Madame Vastra. (AUDIO: A Photograph to Remember)

Behind the scenes
The real Sarah Siddons was an English actress who lived in the late 18th and early 19th centuries, although AUDIO: A Photograph to Remember reveals only that in the Doctor Who universe she was famous and died by the events of the story.