I Capture the Castle is a 2003 British romantic comedy film directed by Tim Fywell. It is based on the 1948 novel of the same name by Dodie Smith, with the screenplay written by Heidi Thomas. The film was released in the UK on 9 May 2003. Romola Garai played the lead role of Cassandra Mortmain alongside Bill Nighy, Rose Byrne and Tara Fitzgerald.