Emma Watson (Harry Potter), Dominic Cooper (Tamara Drewe) and Derek Jacobi (The King’s Speech) have been added to the cast of Simon Curtis’ My Week With Marilyn.

The trio will join Eddie Redmayne, Michelle Williams, Kenneth Branagh, Judi Dench, Zoe Wanamaker, Phillip Jackson and Richard Clifford in the Marilyn Monroe biopic.

My Week With Marilyn will be a documentation of the tense relationship between Lawrence Olivier (Branagh) and Marilyn Monroe (Williams) during the production of The Prince and the Showgirl, as detailed in Colin Clark’s memoirs.

According to ThePlaylist, Watson will play Lucy, a costume assistant who has a brief romance with Clark; Cooper will take on the role of producer Milton Greene; while Jacobi will portray a royal librarian.

My Week With Marilyn is expected to be released toward the end of 2011, which means production should commence in the next few weeks. The film will be Watson’s first post-Harry Potter role.