Two years later, she appeared on screen for the first time in the 2003 television film Boudica (Warrior Queen) and portrayed ill-fated queen consort Catherine Howard in the miniseries Henry VIII.
Her performance in the 2004 drama film My Summer of Love garnered her the Evening Standard British Film Award for Most Promising Newcomer.
The film premiered at the Hamptons International Film Festival in 2005, and debuted on British television in February 2006.
Praised for its "sterling performances," She then featured opposite Meryl Streep and Anne Hathaway in the comedy The Devil Wears Prada, set in the fashion world in New York City.
She went on to perform as Eugenie in Nicholas Wright's Vincent in Brixton at the National Theatre, and as Juliet in Indhu Rubasingham's production of Romeo and Juliet at Chichester Festival Theatre, both in 2002.
2009 also saw Blunt appear in the crime caper comedy Wild Target with Bill Nighy and Rupert Grint.