The dramatic trailer shows Harry (Daniel Radcliffe) engaged in a dark battle to save both the wizard and muggle worlds from the grips of his nemesis Lord Voldemort. Simultaneously he is shown striking up a relationship with his friend Ron Weasley's sister, Ginny, played by Bonnie Wright.
The trailer, which is one of the most popular downloads on the internet, shows the film's opening sequence of the Millennium Bridge in London collapsing. The dramatic scene is the first time one of the film adaptations has deviated significantly from J K Rowling's plot.
Albus Dumbledore, played by Michael Gambon, realises he cannot fight Voldemort alone, so takes Harry under his wing to help. The film's ending also differs from the book to avoid a clash with the ending of the final film Harry Potter and the Deathly Hallows.
The film is not being released in Britain until July 17, two days later than in the US.