|Place of origin:||Earth|
|Appearances:||TV: Inferno, PROSE: Who Killed Kennedy|
|Main actor:||Sheila Dunn|
- You may be looking for the Petra Williams of the Inferno universe.
Petra Williams was Professor Eric Stahlman's assistant at the Inferno Project. She was at first loyal to her employer, but Greg Sutton helped her realise how dangerous the project really was, and she helped the Third Doctor put an end to it. (TV: Inferno)