Defferary's first screen role was in 1992 as Daisy in The Ruth Rendell Mysteries serial "Kissing the Gunner's Daughter".
[3] In 1997 she had a role in Cadfael (Season 3, Episode 2, "St Peter's Fair") as Emma Vernold, and also played "Cicely" in the comedy sketch "Look Listen & Take Heed – Women Keep Your Virtue" on Harry Enfield and Chums.
Her film credits include Red Mercury (Amanda),[7] Pandaemonium (Miss Holland) and I'll Sleep When I'm Dead (Annie, waitress).
As well as screen roles, Defferary has also starred in a number of theatrical productions including The Rivals and The Comedy of Errors, both for the Royal Shakespeare Company.
[2] At the Royal Court Theatre she starred in The Arsonists,[9][10][11] and Push Up alongside David Tennant.