Catherine Tregenna wrote several episodes of Torchwood. She also penned the Doctor Who episode The Woman Who Lived, which made her the fifth woman to write a story for the show and the first since Helen Raynor in 2008.
For Torchwood, she scripted Out of Time, Captain Jack Harkness, Meat and Adam.
Though she sometimes partners with her brother, Jon Tregenna, she has been credited solely for her work on Torchwood and Doctor Who. She is also the only writer to be nominated for a Hugo Award for her work on Torchwood.
Her scripts for the Doctor Who spin-off have all featured significant advancements in the emotional lives of the main characters. In particular, she is responsible for giving Owen Harper his first significant on-screen love affair (Out of Time), introducing Jack's brother (Adam) and his namesake (Captain Jack Harkness) and for revealing Torchwood 3 to Rhys Williams (Meat).