Natalie Dormer has been cast in 'The Hunger Games: Mockingjay'.

The 'Game of Thrones' actress will play Cressida in the final instalments of the fantasy franchise, which will see Suzanne Collins' novel of the same name split across two movies.

The character is a film director from the fictitious Capitol who decides to escape the opulent city to join Katniss Everdeen's rebellion and shoots footage of her as she rallies support in the various poorer districts and fights in a bloody war.

Dormer currently plays Margaery Tyrell on HBO's hit fantasy drama and previously portrayed Anne Boleyn on period drama, 'The Tudors'.

The actress also appeared on US TV show 'Elementary', which is a modern day adaptation of 'Sherlock Holmes', playing Irene Adler.

The latest casting follows news that Julianne Moore may join the final two films as President Coin, the powerful leader of District 13.

Jennifer Lawrence will reprise her role as heroine Katniss and she will be joined by Josh Hutcherson as Peeta Mellark and Liam Hemsworth as Gale Hawthorne.

Francis Lawrence will direct the films for release in November 2014 and November 2015, respectively.

Meanwhile, the next film in the series - 'The Hunger Games: Catching Fire' - is due for release in November.