Dorothy Skerrit

 was Nikola Tesla's secretary in the early 1900s. She met the Thirteenth Doctor, Graham O'Brien, Ryan Sinclair and Yasmin Khan and helped them defeat the Skithra. (TV: Nikola Tesla's Night of Terror)

Behind the Scenes
Dorothy Skerrit was one of Tesla's secretaries in real life. However, the two did not meet until 1912, several years after the episode's setting.