HARRY POTTER AND THE HALF-BLOOD PRINCE ***
THE unwritten rule of Harry Potter movies is that each one promises to be bigger, longer and darker than the last.
With Harry Potter and the Half-Blood Prince receiving its world premiere in London last night, the juggernaut shows little sign of slowing down.
The appetite for Potter films is insatiable, and their value to Hollywood shouldn't be underestimated: with only one book left to adapt, it's small wonder the conclusion to JK Rowling's saga, Harry Potter and the Deathly Hallows, is being turned into two films (they will be released in November 2010 and summer 2011).
All of this means there's a way to go yet before Harry gets to have his fated final showdown with the evil Lord Voldemort.
The good news about Harry Potter and the Half-Blood Prince, though, is that it makes the prospect of another couple of films feel like something to which it's actually worth looking forward.
Returning director David Yates, who will now see the Potter franchise through to its conclusion, seems to have grown in confidence since his first foray into blockbuster filmmaking.
Not only has he made the film look gorgeous, but he has a much surer grip on the special effects, deploying them in the service of big set pieces that actually flow with the rhythms of the story, as well as a better understanding of what his younger cast can do.
Here, he has sensibly curtailed the screen time for the less dramatically skilled, falling back on seasoned actors, such as Alan Rickman and Helena Bonham Carter, to do more of the heavy lifting.
Mercifully, he hasn't had to do that with Daniel Radcliffe, who has taken ownership of Harry, injecting some much-needed wit into the role.
Reflecting Harry's maturing status, The Half-Blood Prince requires him to work even more closely with Dumbledore (Michael Gambon), who needs the lightning-scarred youngster to put his increasing fame in the wizard world to use to coerce some vital information about Voldemort from Hogwarts' name-dropping new potions professor, Horace Slughorn (Jim Broadbent).
A former teacher at the school for witchcraft and wizardry, the dandyish Slughorn prides himself on the famous pupils he has taught, but Dumbledore knows he's hiding a dark secret about his relationship with the young Voldemort, whom we meet in a series of flashbacks that reveal him to be almost as creepy as that kid from The Omen.
Meanwhile, Professor Snape (Rickman) finally starts to reveal what may be his true colours by secretly aligning himself more forcefully with the Dark Arts and taking an active role in looking out for Harry's arch rival, Draco Malfoy (Tom Fenton), who has been chosen by Voldemort to carry out a deadly mission.
If there's a fault with this progressive darkening of the material it's that the weightier, emotional stuff the characters are going through often jars with the more comedic elements built around their exploding hormones.
Meanwhile, the film lags in the middle section, as it spends an inordinate amount of time focusing on the chaste romantic entanglements of Harry, Ron and Hermione, with the majority of attention focused on Rupert Grint's goofy Ron. For some inexplicable reason, he finds himself the object of desire for love-struck new girl Lavender Brown (Jessie Cave), something that blinds him to Hermione's feelings for him. (Emma Watson, sadly, has far less to do this time out.)
For the most part, however, Harry Potter and the Half-Blood Prince succeeds in being a much more immersive film than normal, and comes close to capturing on film some of the texture and richness of Rowling's books.