By Caroline Westbrook
BBC News Online
Harry Potter and the Prisoner of Azkaban, the third in the series of films based on JK Rowling's books, is released in the UK on Monday.
The film is based on the third of JK Rowling's books
One of the most eagerly awaited films of the year, it comes to cinemas under very different circumstances from its predecessors.
For one thing, it's the first Potter outing not to go head-to-head with a Lord of the Rings movie.
Instead, it faces an onslaught of summer blockbusters including Shrek 2 and the Spider-Man sequel.
But perhaps more notable is the departure of Chris Columbus from the director's chair.
Columbus, who made the first two Potter films, has taken on the role of producer and handed the directorial reins to Mexican film-maker Alfonso Cuaron, best known for Y Tu Mama Tambien.
The result is a Potter that is far darker in tone than its predecessors - but that still stays true to the spirit of the book, tempering its scarier moments with some of the most lavish visuals ever to grace the series.
For those unfamiliar with the story, Harry and pals Ron and Hermione return to Hogwarts school for their third year.
But there is danger ahead for Harry in the shape of fugitive Sirius Black, the man who allegedly betrayed the boy wizard's parents to their murderer, Lord Voldemort.
When Black escapes from Azkaban prison and heads for Hogwarts in search of Harry, it is a tense time for all concerned - will Harry's wizarding skills be enough to keep him out of trouble?
Gary Oldman joins the cast as Sirius Black
Like the last two films, Azkaban provides more than its fair share of scares - the Dementors make their debut here and are terrifying in parts.
But it's also a beautiful film, Cuaron's eye for detail giving rise to some genuinely stunning set pieces and special effects.
There are also some terrific performances from the cast newcomers, including Gary Oldman as Black and David Thewlis as the latest Defence Against the Dark Arts teacher, Professor Lupin.
Michael Gambon steps into Richard Harris' shoes as Dumbledore and does a fine job.
But while all the usual elements and characters are present - from the Dursleys to Draco Malfoy - the emphasis is much more on Harry, Ron and Hermoine.
Radcliffe has never been better, and it is a pleasure to see the central trio growing into their roles, as much as the characters are growing with them.
All of which adds up to one of the best films of the summer so far, and one that bodes well for Harry Potter's future on film.