Diana Wright was the owner of a bookshop which also served as a pub. She interrogated the Fifth Doctor thinking he was someone strange. She helped to work out what was going on. She eventually realised she was part of a war and that she was a deserter. (AUDIO: The Bookshop at the End of the World)
The Doctor would eventually discover that Diana, along with many other people throughout history who looked like her, were caused by a group of Time War Daleks who — while on a mission to prevent the rise of Time Lord society on Gallifrey — created a time distortion which created alternate versions of themselves as four un-mutated Kaled people. This time distortion also caused multiple copies of these four Kaleds to appear at various points throughout time and space. (AUDIO: Effect and Cause)