Daniel Radcliffe and Rupert Grint, who play starring roles in the film, were there, and so was Harry Potter author JK Rowling, who signed autographs for fans.
Harry Potter and the Half-Blood Prince, which goes on general release on 15 July, will be followed by two more in the series about the young wizard.
The last book in Rowling’s series, Harry Potter and the Deathly Hallows, has been divided into two parts made for the cinema.
19-year-old Radcliffe admitted that he would miss playing the role of Harry Potter, and 20-year-old Rupert Grint, who plays Ron Weasley, attended the showing despite recovering from a mild bout of swine flu.
