click on images to enlarge
Dorothy Skerrit was Nikola Tesla’s secretary sometime around the 1900s. She met the Thirteenth Doctor, Graham O’Brien, Ryan Sinclair and Yasmin Khan and helped them defeat the Skithra. (Nikola Tesla’s Night of Terror)
BEHIND THE SCENES
Dorothy Skerrit was indeed one of Tesla’s secretaries in the real world. However, the two did not meet until 1912, potentially several years after the episode’s setting, though the exact year is never made clear within the episode.