Duff launched her career on stage before joining the cast of the acclaimed BBC dramedy "Shameless," which brought her a pair of BAFTA nominations. She earned another BAFTA nod for her portrayal of the title character in the miniseries "Elizabeth I: The Virgin Queen" (2005).
Duff's noteworthy film work includes Notes on a Scandal (2006) and her BAFTA-nominated supporting turn as John Lennon's troubled mother in the biographical drama Nowhere Boy (2009). That same year, she played author Leo Tolstoy's daughter (opposite Christopher Plummer and Helen Mirren) in The Last Station.