Warner Brothers have announced that casting is now complete for the new Harry Potter film, The Half Blood Prince. Two award-winning actors will be joining the cast including Jim Broadbent, who will play Potions Professor Horace Slughorn and Helen McCrory (Becoming Jane, The Queen) who will play Draco Malfoy's mother Narcissa Malfoy. Watch a sneak peak behind the scenes of Harry Potter and the Half Blood Prince.