Celia Doras was an Earth girl. She was born in 1910. When a great evil came to her home town of Guernsey on 31 October 1913, the Doctor saved the inhabitants, but could not prevent Celia's death.
When Nazis occupied Guernsey in 1941, the Seventh Doctor convinced Ma Doras to let Bernice Summerfield assume Celia's identity to investigate what had gone wrong with history. (PROSE: Just War)